Template creation: Append slug to template name if a template with a matching name exists

[jameskoster]

This came up in #42165.

The problem

If you have two posts with the same title and create templates for them both, they will have the same name, and you will see this in the templates list:

Clearly there is no way to identify one from the other without opening the template.

A possible solution

For taxonomy templates we append the slug when duplicate names exist, resulting in things like this:

We might consider implementing this solution across the board, or exploring alternatives.

cc @jorgefilipecosta @ntsekouras

[github-actions]

Hi,
This issue has gone 180 days without any activity. This means it is time for a check-in to make sure it is still relevant. If you are still experiencing this issue with the latest versions, you can help the project by responding to confirm the problem and by providing any updated reproduction steps.
Thanks for helping out.