REST API: Support . in theme directory names in WP_REST_Global_Styles_Controller, WP_REST_Templates_Controller, and WP_REST_Themes_Controller.
Regex changes from [52376] are reverted to restore the original regex patterns. Why? [52376] used an include characters pattern, which was too limiting. It did not account for localized characters, such as é, or other valid directory name characters.
The original theme directory regex pattern, i.e. [^.\/]+(?:\/[^.\/]+)? excluded the period . character. Removing the . character resolves the reported issue by allowing matching for themes/theme-dirname-1.0/ or themes/<subdirname>/theme-dirname-1.0/.
As the pattern used an exclude approach, all characters are valid for matching except for /. However, not all characters are cross-platform valid for directory names. For example, the characters /:<>*?"| are not valid on Windows OS. The pattern now excludes those characters.
The theme's directory (or subdirectory) name pattern matching is now used in WP_REST_Global_Styles_Controller, WP_REST_Templates_Controller, and WP_REST_Themes_Controller.
Follow-up to [51003], [52051], [52275], [52376].
Props costdev, hellofromTonya, spacedmonkey, TimothyBlynJacobs, bijayyadav, kafleg.
Fixes #54596.