Split existing templates by the type

Re-roll for 1.1.0 and added sorting by the section name.

Forgot to add accessCheck() method to make it compatible with D10. Please ignore the patch from #4 and use this one instead.

re-roll for 1.1.1

This seems similar to https://www.drupal.org/project/section_library/issues/3195007 ✨ Allow filtering between "Section" & "Template" within offcanvas & modal screen Needs work