Add more tests for Intl.Locale.prototype.getNumberingSystems

[anba]

Add coverage for:

• Language subtag has more than three letters.
• Lookup locale uses prefix matching.
• Unicode extension is present.
• Unicode extension is empty or the string "true".
• "latn" is returned for an unsupported locale.

Also update existing tests and test meta data to match current spec text.

[anba]

• preferred-from-unicode-extension-true-empty.js fails in JSC and V8 because of an ICU4C-related issue.

[github-actions]

6 new or modified tests were run on 7 engines.

View workflow run

Test	Engine262	GraalJS	JavaScriptCore	QuickJS	SpiderMonkey	V8	XS
intl402/Locale/prototype/getNumberingSystems/language-subtag-with-more-than-three-letters.js	❌	✅	✅	❌	✅	✅	❌
intl402/Locale/prototype/getNumberingSystems/lookup-locale-by-prefix.js	❌	✅	✅	❌	✅	✅	❌
intl402/Locale/prototype/getNumberingSystems/output-array.js	❌	✅	✅	❌	✅	✅	❌
intl402/Locale/prototype/getNumberingSystems/preferred-from-unicode-extension-true-empty.js	❌	❌	❌	❌	✅	❌	❌
intl402/Locale/prototype/getNumberingSystems/preferred-from-unicode-extension.js	❌	✅	✅	❌	✅	✅	❌
intl402/Locale/prototype/getNumberingSystems/unsupported-defaults-to-latn.js	❌	✅	✅	❌	✅	✅	❌