Revert gzip compression of URL Metric data

[westonruter]

Summary

Fixes #1928
This reverts #1905

Relevant technical choices

An alternative to this is #1924 which keeps the code to gzip-compression the URL Metric in the codebase, but just disables it by default. However, since I found that Safari and Firefox always fail to send a URL Metric at pagehide when compression is involved, and Chrome also usually fails as well, it seems better to remove this code since it is not safe to use currently. Hopefully this revert can be reverted so we can benefit from gzip compression again!

[github-actions]

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Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: b1ink0 <b1ink0@git.wordpress.org>
Co-authored-by: felixarntz <flixos90@git.wordpress.org>

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.20%. Comparing base (47eef00) to head (b92b042).
Report is 3 commits behind head on release/2025-03-17.

Additional details and impacted files

@@                  Coverage Diff                   @@
##           release/2025-03-17    #1929      +/-   ##
======================================================
- Coverage               71.39%   71.20%   -0.19%     
======================================================
  Files                      86       86              
  Lines                    7043     6998      -45     
======================================================
- Hits                     5028     4983      -45     
  Misses                   2015     2015              

Flag	Coverage Δ
multisite	71.20% <100.00%> (-0.19%)	⬇️
single	40.69% <0.00%> (+0.26%)	⬆️

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[b1ink0]

This test case should be removed.

performance/plugins/optimization-detective/tests/storage/test-class-od-rest-url-metrics-store-endpoint.php

Lines 395 to 412 in ddcd3ae

	'invalid_decoded_json_body_content_length' => array(
	'params' => array_merge(
	$valid_params,
	array(
	// Fill the JSON with more than 1MB of highly compressible data.
	'elements' => array(
	array_merge(
	$valid_element,
	array(
	'xpath' => sprintf( '/HTML/BODY/DIV[@id=\'%s\']/*[1][self::DIV]', str_repeat( 'A', MB_IN_BYTES ) ),
	)
	),
	),
	)
	),
	'expected_status' => 413,
	'expected_code' => 'rest_content_too_large',
	),

[felixarntz]

Thanks @westonruter for catching that.

It's a bummer this needs to be reverted, but we can hopefully reinstate it soon. This is something we can maybe reconsider post-1.0.0, as I don't anticipate it changing the API in any significant way.

I personally agree with your point from the ticket that we should eventually reintroduce this, despite the negative impact on BFCache for users where URL metrics are collected.