Revisions: Add edit link functionality for the wp_template and wp_template_part post types.
In preparation for viewing revisions of templates and template parts in the editor, this set changes adds the _edit_link argument when registering the wp_template and wp_template_part post types. This commit also updates get_edit_post_link to account for the unique edit URLs for these post types.
Finally, this commit also adds new unit tests for the get_edit_post_link function, including tests for the post, wp_template, and wp_template_part post types.
Fixes #57709.
Props andraganescu, spacedmonkey, antonvlasenko, youknowriad, ramonopoly, ironprogrammer, annezazu.