[GENERAL][FIXED] - Fix WHATWG spec violations in URL and URLSearchParams polyfills

[w3di]

Summary

Three spec violations in the URL and URLSearchParams polyfills (Libraries/Blob/):

1. URLSearchParams.size returned the number of unique keys (Map.size) instead of the total number of name-value pairs. Per WHATWG spec, .size must return the list's total size.

2. URLSearchParams string constructor split on every = character, silently dropping parts of values containing = (e.g. base64 tokens, JWTs). Per WHATWG spec, only the first = is the key-value separator.

3. URL.hash getter used a regex /#([^/]*)/ that stopped matching at /, breaking fragment identifiers like #/users/123 common in SPA hash-routing. Per WHATWG spec, the hash includes everything from # to end of string.

Changelog:

[General] [Fixed] - Fix WHATWG spec violations in URL and URLSearchParams polyfills

Test Plan

• Updated existing test: URLSearchParams constructed from array with duplicate keys now expects size to be 3 (total pairs) instead of 2 (unique keys).
• All existing tests pass: yarn jest packages/react-native/Libraries/Blob/__tests__/URL-test.js
• Prettier and ESLint checks pass.
• Verified browser behavior matches the fix:

// Browser console (Chrome/Firefox/Safari):
new URLSearchParams([['a','1'],['a','2'],['b','3']]).size // 3
new URLSearchParams('token=abc=def').get('token')         // 'abc=def'
new URL('https://example.com/#/users/123').hash           // '#/users/123'