Includes:
* Renaming the function to `wp_get_last_revision_id_and_total_count()`.
* Making the default value for `$post` consistent with `wp_get_post_revisions()`.
* Making `WP_Error` codes more specific and using them in test assertions.
* Adjusting the function description per the documentation standards.
Follow-up to [53759].
Props JustinSainton, SergeyBiryukov.
See #55857.
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