Add bundled OpenSSL backend for uv Python

[river-walras]

Summary

• add an opt-in/auto-detected bundled OpenSSL backend for Python builds that cannot expose a dynamic libssl, such as uv python-build-standalone
• add aiofastnet.SSLContext to record unrecoverable SSLContext configuration for replay onto aiofastnet's own SSL_CTX
• add server-context preflight, bundled ALPN handling, verify flag copying, cache invalidation, and bundled-backend test coverage

Validation

• UV_CACHE_DIR=/tmp/uv-cache uv run pytest tests/test_ssl_object.py -q
• UV_CACHE_DIR=/tmp/uv-cache uv run ruff check .
• git diff --check

[tarasko]

Thank you for the PR. I need to carefully review it.

One thing that I noticed, instead of downloading, I'd like to have a git submodule link to openssl inside of vendor/ folder and build it there.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 18.42105% with 186 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.22%. Comparing base (6d47711) to head (f443dc3).

Files with missing lines	Patch %	Lines
aiofastnet/ssl_object.pyx	14.64%	169 Missing ⚠️
aiofastnet/_sslcontext.py	35.00%	13 Missing ⚠️
aiofastnet/openssl_compat.py	55.55%	3 Missing and 1 partial ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #39      +/-   ##
==========================================
- Coverage   92.29%   86.22%   -6.07%     
==========================================
  Files          12       13       +1     
  Lines        2426     2636     +210     
  Branches       15       15              
==========================================
+ Hits         2239     2273      +34     
- Misses        183      359     +176     
  Partials        4        4              

Flag	Coverage Δ
Linux	83.72% <18.42%> (-5.97%)	⬇️
Windows	79.54% <18.42%> (-5.72%)	⬇️
macOS	81.09% <18.42%> (-5.74%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 34 untouched benchmarks

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_{Comparing river-walras:bundled-openssl-uv-python (f443dc3) with master (6d47711)}