Add filter state receive_before_connect to tcp_proxy

[akshita31]

Commit Message: This PR picks up the work done in https://github.com/envoyproxy/envoy/pull/25804.

1. It adds a receive_before_connect filter state which can be read by TCP_PROXY and if set TCP_PROXY will not disable downstream reads until the upstream connection is established. This can hence be used by filters before TCP_PROXY to set the filter state in initializeReadFilterCallbacks, and then StopIteration in onNewConnection and onData, until they have read the required amount of data before upstream connection establishment.
2. Based on feedback in #25804 , this PR adds a flow control to prevent early_data_buffer from overflowing, by disabling downstream reads on early data until the upstream connection establishment is finished.
3. Adds integration and unit tests to cover the newly added functionality.

Additional Description: Risk Level: Low Testing: Added integration and unit tests Docs Changes: Done 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[bot]]

Hi @akshita31, 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.

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/36581 was opened by akshita31.

see: more, trace.

[repokitteh-read-only[bot]]

As a reminder, PRs marked as draft will not be automatically assigned reviewers, or be handled by maintainer-oncall triage.

Please mark your PR as ready when you want it to be reviewed!

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/36581 was opened by akshita31.

see: more, trace.

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in 7 days if no further activity occurs. Please feel free to give a status update now, ping for review, or re-open when it's ready. Thank you for your contributions!

[github-actions[bot]]

This pull request has been automatically closed because it has not had activity in the last 37 days. Please feel free to give a status update now, ping for review, or re-open when it's ready. Thank you for your contributions!