Template bulk actions

[jameskoster]

Now that we're making it possible to create more types of templates, the number of actions you might want to perform on multiple templates concurrently is increasing.

It would good to explore options for applying these actions to more than one template at a time.

Some examples to consider:

• I want to delete all the templates I created myself.
• I want to clear all customisations made to existing templates.
• I want to merge all my templates with their associated updates (Merge a template update in a theme with your customised version of that same template #41764).
• I want to 'restore factory settings' (essentially all of the above combined).
• I want to rename multiple templates

cc @WordPress/gutenberg-design

[paaljoachim]

Linking in the following issues I have earlier made which gives some UI suggestions.

Templates and Template Parts screens - Provide a way for users to add a description to custom templates.
#36664

Templates screen - add the ability to sort by recently updated, alphabetical, or type (adding additional columns).
#39307

Templates list screen - Adding duplicate to 3 dot menu.
#36665