Introduces:
- New function: `wp_opcache_invalidate_directory()`, to recursively call `wp_opcache_invalidate()` after overwriting .php files.
- New function: `move_dir()`, similar to `copy_dir()` that uses `WP_Filesystem::move()` followed by `wp_opcache_invalidate_directory()`, and has a fallback to `copy_dir()`.
Props: costdev, afragen, peterwilsoncc, sergeybiryukov, ironprogrammer, flixos90, bronsonquick, mukesh27, azaozz.
Fixes#57375.
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