Preserve whitespace in array settings

[missusk]

Fixes #1096.

wp_cache_setting() collapsed every whitespace run in an exported array, including whitespace inside its string values. This keeps the setting on one physical line while compacting only var_export()'s layout whitespace, so string values round-trip unchanged.

Testing

• PHP smoke suite: 89 tests, 118 assertions
• WordPress integration suite: 53 tests, 148 assertions
• PHPCS on changed lines
• Confirmed the previous implementation collapses spaces, tabs and line breaks; this change preserves them byte-for-byte while keeping the config entry on one physical line

Release Notes

• Fix: preserve whitespace inside array settings written to the cache configuration.