Tests: Delete attachment files during test cleanup

[SirLouen]

Delete attachment files before _delete_all_data() clears the database tables. Calling wp_delete_attachment( $id, true ) while attachment metadata still exists removes the uploaded file and its associated image files. Other records retain the existing bulk SQL cleanup.

This refreshes the original patch for https://core.trac.wordpress.org/ticket/41978 against current trunk without rewriting the PR history. The attachment query now returns scalar IDs, and the regression test verifies that an existing uploaded file and its attachment post are deleted.

Validation

Validated on 640c25f:

• Focused PHPUnit test passed in single-site and multisite: 1 test, 3 assertions each.
• PHPCS passed both changed files.
• Removing the attachment cleanup loop made the regression test fail because the uploaded file remained.
• A randomized media/image run with seed 8898 produced 864 tests and 2,425 assertions, with 7 skips and two failures. The exact trunk baseline produced the same two failures: a caption-output assertion and a URL-based image crop reporting a missing file. Neither is introduced by this change.
• That single diagnostic run took 40.530 seconds with the patch and 41.453 seconds on trunk. The extra attachment query runs once per class teardown; longer-term suite timing can be monitored through CodeVitals.
• The patch applies cleanly to SVN trunk, including the new regression-test file.

Fresh CI is running on the refreshed head.

Use of AI tools

AI assistance for this refresh: Yes
Tool(s): Codex
Model(s): GPT-6, GPT-5.6
Used for: Reviewing the existing patch, refreshing the branch, simplifying the query, correcting the regression test, running validation, and drafting this update.

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This pull request is for code review only. Please keep other discussion in the Trac ticket. Do not merge this pull request.

[github-actions]

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Props sirlouen, lancewillett.

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[github-actions]

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[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 63586
GitHub commit: 2c6ec19

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.