upgrade tokio 1.34 => 1.36

[problame]

tokio 1.36 has been out for a month.

Release notes don't indicate major changes.

Skimming through their issue tracker, I can't find open C-bug issues that would affect us.

(My personal motivation for this is JoinSet::try_join_next.)

[conradludgate]

Proxy recently forked copy_bidirectional, which had some changes since. Notably only cooperative budget stuff. Potentially need to make some changes there, but nothing blocking tokio-rs/tokio#6250

[github-actions]

2484 tests run: 2362 passed, 0 failed, 122 skipped (full report)

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Flaky tests (1)

Postgres 14

• test_pg_regress[4]: debug

Code coverage* (full report)

• functions: 28.7% (6935 of 24172 functions)
• lines: 47.2% (42529 of 90097 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
762828e at 2024-03-04T16:52:22.559Z :recycle:}