fetch: improve regexes in data-uri.js

[Uzlopak]

sonarjs was reporting some imperformance in the regexes

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[Copilot]

Pull Request Overview

This PR improves regex patterns in the data-url.js file to address performance issues identified by SonarJS. The changes focus on optimizing regex patterns and refactoring a for loop to a while loop.

• Adds the u flag to regex patterns for better Unicode handling and performance
• Optimizes character class ordering and grouping in regex patterns
• Refactors a for loop to a while loop in the percentDecode function

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@7321451). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4483   +/-   ##
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  Coverage        ?   92.94%           
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  Files           ?      106           
  Lines           ?    32976           
  Branches        ?        0           
=======================================
  Hits            ?    30649           
  Misses          ?     2327           
  Partials        ?        0           

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