Tests: Restore locale without post-rollback queries - #13189

Summary

• Initializes WP_Scripts before case-specific URL filters and restores locale state around privacy and user-request email fixtures.
• Captures a clean site locale during setup and restores the locale global and translation controller after transaction rollback without querying options.
• Avoids opening a new parent transaction that can metadata-lock separate-process test installation.
• Keeps the source changes confined to PHPUnit tests and fixtures.

Verification

• Replayed the original l10n failure and the Ajax and formatting seeds that previously hung at separate-process tests.
• 100 consecutive fresh randomized l10n-group runs passed on the combined campaign head with the same locale implementation; each completed 266 tests and 804 assertions with the known warning. That gate head also contained an unrelated permalink teardown reset omitted from this isolated PR.
• 100 consecutive fresh randomized Ajax-group runs also passed; each completed 190 tests and 1,212 assertions with one skip.
• Seeds 1789060001 through 1789060100 covered the final l10n proof; Ajax seeds 1789050001 through 1789050100 covered the metadata-lock regression.
• PHP syntax checks and git diff --check passed.

Trac: https://core.trac.wordpress.org/ticket/65893