proxy: swap tungstenite for a simpler impl

[conradludgate]

Problem

I wanted to do a deep dive of the tungstenite codebase. tokio-tungstenite is incredibly convoluted... In my searching I found fastwebsockets by deno, but it wasn't quite sufficient.

This also removes the default 16MB/64MB frame/message size limitation. framed-websockets solves this by inserting continuation frames for partially received messages, so the whole message does not need to be entirely read into memory.

Summary of changes

I took the fastwebsockets code as a starting off point and rewrote it to be simpler, server-only, and be poll-based to support our Read/Write wrappers.

I have replaced our tungstenite code with my framed-websockets fork.

https://github.com/neondatabase/framed-websockets

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]

3084 tests run: 2957 passed, 0 failed, 127 skipped (full report)

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Flaky tests (1)

Postgres 16

• test_fixture_restart: debug

Code coverage* (full report)

• functions: 31.5% (6349 of 20174 functions)
• lines: 47.5% (47926 of 100928 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
a8e45d1 at 2024-05-15T15:24:34.392Z :recycle:}