Add gRPC middleware Context-aware interfaces

[jmacd]

Description

The gRPC middleware interface does not support initializing context-aware middleware. This requires a new method for both client and server.

Link to tracking issue

Fixes #14523

Testing

✅

Documentation

✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.85%. Comparing base (88735a1) to head (f6dd450).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14525      +/-   ##
==========================================
- Coverage   91.86%   91.85%   -0.01%     
==========================================
  Files         677      677              
  Lines       42705    42723      +18     
==========================================
+ Hits        39229    39244      +15     
- Misses       2423     2425       +2     
- Partials     1053     1054       +1     

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[codspeed-hq]

Merging this PR will degrade performance by 32.68%

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

❌ 1 regressed benchmark
✅ 60 untouched benchmarks
⏩ 20 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	HTTP/2.0,_client_per_thread_(like_single_app)	1.1 ms	1.6 ms	-32.68%

---

_{Comparing jmacd:jmacd/middleware_context (f6dd450) with main (88735a1)}

Footnotes

1. 20 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[bogdandrutu]

Should we deprecate the non-context and eventually remove since this is not a stable package?

[jmacd]

I assumed this was stable because configmiddleware was stabilized.
(How can extensionmiddleware not be stable if configmiddleware is?)

I would say yes, we can remove these if technically unstable. I was motivated to really understand how we add new extension APIs, and I think this also demonstrates that capability.

[jmacd]

In favor of #14536