feat(intl): implement Number.prototype.toLocaleString with Intl support

[alienx5499]

This Pull Request fixes/closes #5074.

It changes the following:

• Implement Number.prototype.toLocaleString([locales [, options]]) using Intl.NumberFormat when the intl feature is enabled, following the same pattern as BigInt.prototype.toLocaleString.
• Return "NaN", "Infinity", and "-Infinity" for non-finite values instead of going through Decimal::try_from_f64.
• Keep the existing fallback behaviour (simple number string conversion) when the intl feature is disabled.
• Add shared tests for 0, 5, -25, NaN, Infinity, -Infinity.
• Add #[cfg(feature = "intl")] tests for locale formatting (en-US, de-DE) and options (useGrouping, minimumFractionDigits).

Testing:

• cargo test -p boa_engine --lib -- number::tests::to_locale_string (without intl)
• cargo test -p boa_engine --features intl_bundled --lib -- number::tests::to_locale_string (with intl)

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,070	49,936	-134
Ignored	2,072	2,207	+135
Failed	821	820	-1
Panics	0	0	0
Conformance	94.54%	94.28%	-0.25%

Fixed tests (1):

test/intl402/Number/prototype/toLocaleString/throws-same-exceptions-as-NumberFormat.js (previously Failed)

Tested main commit: baaadfeeaf4a64f34e82cbbb9fee3ed4013495c0
Tested PR commit: 5e7c73ebe26721092c75374c1ea7ce3ad6dea416
Compare commits: baaadfe...5e7c73e

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.35%. Comparing base (6ddc2b4) to head (5e7c73e).
⚠️ Report is 867 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5078       +/-   ##
===========================================
+ Coverage   47.24%   59.35%   +12.11%     
===========================================
  Files         476      563       +87     
  Lines       46892    62678    +15786     
===========================================
+ Hits        22154    37205    +15051     
- Misses      24738    25473      +735     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[alienx5499]

Hi @jedel1043,

Whenever you have a moment, could you please take a look at this PR? I’d really appreciate your review.

Thanks!

[jedel1043]

Note for the future: there are technically internationalized versions of non-finite f64 values, but supporting this might be blocked by unicode-org/icu4x#862.

[jedel1043]

Looks good!