Add E2E test of instance audit event streaming

Description of the test

E2E test of instance audit event streaming: gitlab-org/quality/testcases#4080 (closed)

• Includes QA::EE::Resource::InstanceAuditEventExternalDestination to wrap the GraphQL API for instance audit event streaming destinations
• Allow Smocker to be used via a non-loopback IP address
• Tests a few audit event types (more comprehensive cover at lower test levels)

Note: The new resource isn't removed by the test resources handler because it doesn't handle GraphQL yet.

How to set up and validate locally

From the qa directory:

bundle install
bundle exec bin/qa Test::Instance::All http://gdk.test:3000 -- qa/specs/features/ee/api/10_govern/instance_audit_event_streaming_spec.rb

Checklist

• Confirm the test has a testcase: tag linking to an existing test case in the test case project.
• [-] Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Most resources will be cleaned up via the general cleanup task. Check that is successful, or ensure resources are cleaned up in the test:
  • New resources have api_get_path and api_delete_path implemented if possible.
  • If any resource cannot be deleted in the general delete task, make sure it is ignored.
  • If any resource cannot be deleted in the general delete task, remove it in the test (e.g., in an after block).
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• [-] If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• [-] (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK
• If the test requires an admin's personal access token, ensure that the test passes on your local environment with and without the GITLAB_QA_ADMIN_ACCESS_TOKEN provided.