Let patterns decide which custom page template to use

[carolinan]

What problem does this address?

In Twenty Twenty-Five there are some landing page patterns that are only available when the users selects "Add new page".
These landing pages are designed to use a custom page template, that, compared to the standard page template, does not have a post title block.
But when the user inserts the pattern, they have to manually select the intended page template.
It would be helpful to automatically set the page template (but still allow users to update it), perhaps with a new parameter in the pattern registration.