Permalinks: Ignore malformed post type query arrays

[dhrupo]

Trac ticket: https://core.trac.wordpress.org/ticket/65123

Summary

This ignores non-scalar values when sanitizing post_type query vars in WP::parse_request(), preventing malformed array input from surfacing PHP warnings during front-end requests.

Testing Instructions

1. Request /?post_type[][]=page&post_type[]=post on a local site with WP_DEBUG_DISPLAY enabled.
2. Confirm no warning is emitted before the page output.
3. Run npm run test:php -- --filter Tests_WP_ParseRequest.

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Props dhrupo, mukesh27.

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[mukeshpanchal27]

Let’s use a single test with a data provider for better coverage, and we can remove the duplicate code.

[dhrupo]

Updated in 6b6be36. I collapsed the GET/POST cases into a single provider-backed test and removed the duplicated setup/cleanup code. I also reran npm run test:php -- --filter Tests_WP_ParseRequest and ./vendor/bin/phpcs --standard=phpcs.xml.dist tests/phpunit/tests/wp/parseRequest.php after the refactor.