Handle SSLError in TCP comm

[jacobtomlinson]

Closes #8936

It's been a couple of months since #8936 was opened and test_tls_comm_closed_implicit is still failing pretty consistently in CI with openssl==3.4.0.

It's still not clear whether this new SSLError that gets raised should be caught by Tornado, but I had a go at making the error handling more robust to SSLErrors.

This change assumes that SSLErrors that aren't UNKNOWN_CA are non-fatal.

• Tests added / passed
• Passes pre-commit run --all-files

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    26 files   -     1      26 suites   - 1   11h 15m 8s ⏱️ - 15m 0s
 4 112 tests ±    0   4 000 ✅ +    2    111 💤 ± 0  1 ❌  - 2 
50 156 runs   - 1 407  47 914 ✅  - 1 356  2 241 💤  - 47  1 ❌  - 4 

For more details on these failures, see this check.

Results for commit c7c1ba0. ± Comparison against base commit c2ba834.

[fjetter]

Thank you! Incredible that all of your test jobs are green

[jacobtomlinson]

I did rerun a couple of unrelated failures, but yeah exciting that things are pretty much all green for once!