Sanitize the plugin path in `_get_plugin_data_markup_translate()` to a WP_PLUGIN_DIR-relative path. The function is designed in mind for receiving relative paths, but may be used with a absolute path.
This change makes the function path-agnostic, and can accept either relative or absolute (converting to relative internally). Fixes #20813

Built from https://develop.svn.wordpress.org/trunk@25081


git-svn-id: http://core.svn.wordpress.org/trunk@25066 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Theme Installer/Updater: Handle custom Theme directories when updating themes, and installing new themes. Fixes #22501

Built from https://develop.svn.wordpress.org/trunk@25082


git-svn-id: http://core.svn.wordpress.org/trunk@25067 1a063a9b-81f0-0310-95a4-ce76da25c4cd