Add filter to array of template files to locate

[johnbillion]

It's not possible to modify the array of template files that's looped over in order to locate the template file to use on a site.

These arrays are set in the various get_whatever_template() functions (eg get_taxonomy_template(), get_archive_template(), get_home_template()).

A theme framework I'm building adds several new possible template files. Some of these have higher priority than existing templates, and some have lower. Currently I have to use the template_include filter and pass an array of possible template files through locate_template() again due to the varying priority of the templates.

If there was a filter on the array used in get_query_template() this would be easy and would remove the need for locate_template() to be called twice.

Patch

#14310