Tests: Reset locale fixtures after email tests

[sirreal]

Summary

• Initializes WP_Scripts before case-specific URL filters and re-primes locale state around privacy and user-request email fixtures.
• Keeps the changes confined to PHPUnit tests and fixtures.

Verification

• 50 consecutive randomized l10n-group runs passed; each completed 266 tests and 804 assertions.
• Replayed the original failing seed and focused contaminator/consumer cases during diagnosis.
• PHP syntax checks passed for every changed PHP file.
• git diff --check passed.

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