proxy: add websocket regression tests

[conradludgate]

Problem

We have no regression tests for websocket flow

Summary of changes

Add a hacky implementation of the postgres protocol over websockets just to verify the protocol behaviour does not regress over time.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2664 tests run: 2539 passed, 0 failed, 125 skipped (full report)

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Code coverage* (full report)

• functions: 28.4% (7031 of 24721 functions)
• lines: 47.2% (43457 of 92118 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
458c88a at 2024-03-14T15:02:03.783Z :recycle:}