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python: introduce Asynchronous QMP package

GitLab: https://gitlab.com/jsnow/qemu/-/commits/python-async-qmp-aqmp
CI: https://gitlab.com/jsnow/qemu/-/pipelines/330003554
Docs: https://people.redhat.com/~jsnow/sphinx/html/qemu.aqmp.html
Based-on: <20210701020921.1679468-1-jsnow@redhat.com>
          [PULL 00/15] Python patches

Hi!

This patch series adds an Asynchronous QMP package to the Python
library. It offers a few improvements over the previous library:

- out-of-band support
- true asynchronous event support
- avoids undocumented interfaces abusing non-blocking sockets

This library serves as the basis for a new qmp-shell program that will
offer improved reconnection support, true asynchronous display of
events, VM and job status update notifiers, and so on.

My intent is to eventually publish this library directly to PyPI as a
standalone package. I would like to phase out our usage of the old QMP
library over time; eventually replacing it entirely with this one.

This series looks big by line count, but it's *mostly*
docstrings. Seriously!

This package has *no* external dependencies whatsoever.

Notes & Design
==============

Here are some notes on the design of how the library works, to serve as
a primer for review; however I also **highly recommend** browsing the
generated Sphinx documentation for this series.

Here's that link again:
https://people.redhat.com/~jsnow/sphinx/html/qemu.aqmp.html

The core machinery is split between the AsyncProtocol and QMP
classes. AsyncProtocol provides the generic machinery, while QMP
provides the QMP-specific details.

The design uses two independent coroutines that act as the "bottom
half", a writer task and a reader task. These tasks run for the duration
of the connection and independently send and receive messages,
respectively.

A third task, disconnect, is scheduled asynchronously whenever an
unrecoverable error occurs and facilitates coalescing of the other two
tasks.

This diagram for how execute() operates may be helpful for understanding
how AsyncProtocol is laid out. The arrows indicate the direction of a
QMP message; the long horizontal dash indicates the separation between
the upper and lower half of the event loop. The queue mechanisms between
both dashes serve as the intermediaries between the upper and lower
half.

                       +---------+
                       | caller  |
                       +---------+
                           ^ |
                           | v
                       +---------+
     +---------------> |execute()| -----------+
     |                 +---------+            |
     |                                        |
[-----------------------------------------------------------]
     |                                        |
     |                                        v
+----+------+    +----------------+    +------+-------+
| ExecQueue |    | EventListeners |    |Outbound Queue|
+----+------+    +----+-----------+    +------+-------+
     ^                ^                       |
     |                |                       |
[-----------------------------------------------------------]
     |                |                       |
     |                |                       v
  +--+----------------+---+       +-----------+-----------+
  | Reader Task/Coroutine |       | Writer Task/Coroutine |
  +-----------+-----------+       +-----------+-----------+
              ^                               |
              |                               v
        +-----+------+                  +-----+------+
        |StreamReader|                  |StreamWriter|
        +------------+                  +------------+

The caller will invoke execute(), which in turn will deposit a message
in the outbound send queue. This will wake up the writer task, which
well send the message over the wire.

The execute() method will then yield to wait for a reply delivered to an
execution queue created solely for that execute statement.

When a message arrives, the Reader task will unblock and route the
message either to the EventListener subsystem, or place it in the
appropriate pending execution queue.

Once a message is placed in the pending execution queue, execute() will
unblock and the execution will conclude, returning the result of the RPC
call to the caller.

Ugly Bits
=========

- MultiException is ... wonky. I am still working out how to avoid needing it.
  See patch 04/20 for details here, or see
  https://people.redhat.com/~jsnow/sphinx/html/qemu.aqmp.error.html

  Patch 06/20 also goes into details of the ugliness; see
  AsyncProtocol._results or view the same information here:
  https://people.redhat.com/~jsnow/sphinx/html/_modules/qemu/aqmp/protocol.html#AsyncProtocol._results

- There are quite a few lingering questions I have over the design of the
  EventListener subsystem; I wrote about those ugly bits in excruciating detail
  in patch 14/20.

  You can view them formatted nicely here:
  https://people.redhat.com/~jsnow/sphinx/html/qemu.aqmp.events.html#experimental-interfaces-design-issues

Patch Layout
============

Patches 1-2 are tiny pylint configuration changes.
Patches 3-5 begin to check in Async QMP components, they are small.
Patches 6-11 add a generic async message-based protocol class,
             AsyncProto. They are split as small as I could
             reasonably split them.
Patches 12-14 check in more QMP-specific components.
Patches 15-18 add qmp_protocol.py, the new 'QMP' class. They're split as
              far down as I could, I hope they're easy to review.
Patches 19-20 add a few finishing touches, they are small patches.

Future Work
===========

These items are in progress:

- A Synchronous QMP wrapper that allows this library to be easily used
  from non-async code; this will also allow me to prove it works well by
  demoing its replacement throughout iotests.

- A QMP server class; to facilitate writing of unit tests.

- Unit tests. Real unit tests.

If you made it this far in the cover letter, congrats :)

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slirp CVE-2021-3592/3593/3594/3595

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1970850
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1970858
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1970842
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1970823
BRANCH: rhel-av-8.5.0
BREW: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=37588329

qapi: untie 'if' conditions from C preprocessor

Hi,

This series makes the 'if' conditions less liberal, by formalizing a simple
expression tree based on bare boolean logic of configure option identifiers.

(this allows to express conditions in Rust in my QAPI-Rust PoC series)

thanks

v6: after Markus review
 - drop the predicate tree, QAPISchemaIfCond simply holds the original object
 - introduce the dict operations ('all', 'any', 'not') in multiple patches
 - split QAPISchemaIfCond introduction in multiple patches
 - replace __bool__ usage with is_present()
 - removed __eq__
 - move cgen/docgen implementation to common.py
 - doc & commit message updates
 - rebased

v5:
 - drop the [ COND, ... ] sugar form
 - move documentation update as first patch
 - documentation and commit message tweaks

v4:
 - keep gen_if/gen_endif in common.py, reducing C codegen in schema.py
 - raise NotImplemented instead of False for unhandled __eq__
 - change check_if() to keep the json/raw form, add _make_if() to build a
   QAPISchemaIfCond
 - improve __repr__ usage
 - drop ABC usage
 - tweaks here and there
 - add various commit tags

v3:
 - rebasing on queued pt4 (after waiting for it to land)
 - improve documentation generation, to be more human-friendly
 - drop typing annotations from schema.py (not yet queued)
 - commit message tweaks

v2:
 - fix the normalization step to handle recursive expr
 - replace IfCond by QAPISchemaIf (JohnS)
 - commit message and documentation tweaks
 - mypy/flake8/isort

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qga: public ssh injection api support

BZ: 1967716
BRANCH: rhel-8.5.0
UPSTREAM: merged
BREW: 37334432

Straightforward backport, with a few minor conflicts.

Note: the unit tests are not being run in rhel8, as they require glib 2.60
G_TEST_OPTION_ISOLATE_DIRS. Rely on QA testing.

qapi: untie 'if' conditions from C preprocessor

Hi,

This series makes the 'if' conditions less liberal, by formalizing a simple
expression tree based on bare boolean logic of configure option identifiers.

(this allows to express conditions in Rust in my QAPI-Rust PoC series)

thanks

v5:
 - drop the [ COND, ... ] sugar form
 - move documentation update as first patch
 - documentation and commit message tweaks

v4:
 - keep gen_if/gen_endif in common.py, reducing C codegen in schema.py
 - raise NotImplemented instead of False for unhandled __eq__
 - change check_if() to keep the json/raw form, add _make_if() to build a
   QAPISchemaIfCond
 - improve __repr__ usage
 - drop ABC usage
 - tweaks here and there
 - add various commit tags

v3:
 - rebasing on queued pt4 (after waiting for it to land)
 - improve documentation generation, to be more human-friendly
 - drop typing annotations from schema.py (not yet queued)
 - commit message tweaks

v2:
 - fix the normalization step to handle recursive expr
 - replace IfCond by QAPISchemaIf (JohnS)
 - commit message and documentation tweaks
 - mypy/flake8/isort

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