Add HTMLRewriter class in Python SDK

[ryanking13]

This adds HTMLRewriter class in Python SDK, which does proxy lifetime handling internally.

We have an example that uses HTMLRewriter, but it uses JS API directly which is slightly annoying to use in Python because of the proxy handling.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.01%. Comparing base (66745cd) to head (4f0e824).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5945   +/-   ##
=======================================
  Coverage   70.01%   70.01%           
=======================================
  Files         406      406           
  Lines      107106   107106           
  Branches    17965    17965           
=======================================
+ Hits        74988    74993    +5     
+ Misses      21321    21319    -2     
+ Partials    10797    10794    -3     

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[codspeed-hq]

Merging this PR will improve performance by ×41

⚡ 1 improved benchmark
✅ 69 untouched benchmarks
⏩ 129 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	nullBodyWithStatus[Response]	410.2 µs	10.1 µs	×41

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_{Comparing gyeongjae/htmlrewriter-2 (d386d66) with main (7b9462c)}

Footnotes

1. 129 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. ↩