Connection upgrade support
This MR implements HTTP Upgrade support as defined in https://httpwg.org/specs/rfc7230.html#header.upgrade. Most logic lives in InboundHttpToOutboundGrpc
and InboundGrpcToOutboundHttp
types.
Relates to gitlab-org/gitlab#346248 (closed).
MR overview video https://youtu.be/3jLFjie0lL8
Edited by Mikhail Mazurskiy