Ability to disable/remove “Blank page” template on page creation UI

When creating a new page, the "Blank Page" template is displayed. However, it is not listed in the template overview. It would be useful that an admin is able to disable/remove the “Blank page” template on page creation UI.

An example of usage need: currently, the "Blank Page" template is automatically selected as the default template. You don't have the possibility to remove it so that users don't consider using it, or to replace the current default.

Thus, there would be 2 main needs:
1. To be able to remove/disable the "Blank Page" template
2. To be able to replace it with a different default template (I created ticket XWIKI-24573).