fix(context-replacement): only apply changes when regex matches

[agneym]

Summary

• Fixed bug where ContextReplacementPlugin applied transformations to all require.context() calls regardless of regex match
• The regex check was incorrectly placed inside the new_content_resource conditional, causing recursive, regExp, and critical modifications to apply to non-matching contexts
• Now all transformations only apply when the configured regex successfully matches the request

Test plan

• Added test case context-replacement/non-matching-regex that verifies non-matching contexts are not affected
• Existing context-replacement tests should continue to pass

Closes #12656

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[codspeed-hq]

Merging this PR will not alter performance

✅ 16 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing agneym:fix/context-replacement-regex-matching (2c9cfd8) with main (d02192f)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[chenjiahan]

Thank you! ❤️

[agneym]

@chenjiahan @SyMind rebased with main branch since some unexpected test failures