Media:

- Introduce `wp_image_file_matches_image_meta()` utility function to check whether the image meta (retrieved by attachment ID) matches an image path or URI. A mismatch may happen in some cases, for example after the posts have been exported from one website and imported in another.
- Add unit tests for the new function.
- Improve `wp_image_src_get_dimensions()` a bit and use the new function to prevent these edge cases.

Fixes #50543.
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git-svn-id: https://core.svn.wordpress.org/trunk@48098 1a063a9b-81f0-0310-95a4-ce76da25c4cd