reverse connection: code changes for reverse conn http filter

[basundhara-c]

Commit Message: The reverse_conn http filter serves as the common API endpoint servicing reverse connection related requests as described in this github issue. On upstream(responder) envoy, It accepts reverse connection requests from initiator envoy. On both upstream and downstream envoy, it responds to GET calls for reverse connection related statistics. This filter should be attached to a listener and must be present in the config for both upstream and downstream envoy. This PR is strictly tied with #37368.
Additional Description:
Risk Level:
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional API Considerations:]

[repokitteh-read-only]

Hi @basundhara-c, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #37822 was opened by basundhara-c.

see: more, trace.

[zuercher]

@botengyao are you able to look at this (and the other related PRs)?

[botengyao]

@zuercher yes, I will take a look at the core PR at first today.

[botengyao]

@zuercher These are mainly contrib changes, I think the plan is to review envoy core changes #37368 at first with the side review of the implementation in contrib. These are highly combined together in terms of interface. And then we can focus back to the details of these contrib PRs. I'd like to wait-any these at first for contrib changes.

/wait-any