Update get_plugin_data()

[nacin]

#20103 started with taking get_plugin_data() and _get_plugin_data_markup_translate() and applying the same concept to themes. Eventually I discarded that approach, but not before I had fixed up both of these functions.

Attached is a patch.

[nacin]

The one issue with 20266.diff​ is that it causes sanitized data to be cached (as _get_plugin_data_markup_translate() is run even when $markup = $translate = false), but then will still re-sanitize the data when _get_plugin_data_markup_translate() is used later to apply markup or apply translations.

We probably need a final sanitize = false parameter, then call sanitize = true in get_plugins(). (Or true by default and false where we don't need it.) In general, these kinds of issues were what caused WP_Theme to be written.

[nacin]

In [20229]:

Clean up get_plugin_data() and _get_plugin_data_markup_translate(), and standardize sanitization. fixes #20266.

[kawauso]

Related: #16418