Tests: Prevent state leaks in functions tests

[sirreal]

Summary

• Resets the forced-SSL function-static fixture and resynchronizes timezone-choice translation state after locale-changing data sets.
• Keeps the changes confined to PHPUnit tests and fixtures.

Verification

• 50 consecutive randomized functions-group runs passed; each completed 1,212 tests and 2,499 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