Extend uuid API for D9+ and provide maintainership for this

Problem/Motivation

I currently work on several contrib and custom modules which should be uuid only including their canonical routes etc. I also work on a module to extend core user entity in the way the users can't know their uid. Especially the user-uuid-only solution is probably something which will always be a contrib module. But all of my projects have the same base problem: They need some extra API I currently need to copy between them. So I can wait to solve this sometime in future or just move the extra api to a central contrib module. I think this namespace would be fine for this.
I also just added a comment to the long lasting issue ✨ Make it possible to link to an entity by UUID Active to stay at first focused on entity paths.

Proposed resolution

I can and like to do many of this work by my own when I can be the added as co-maintainer. My focus will we a new 2.x.x Branch for D9+.
The first reusable API things I like to add are a reusable uuid ParamConverter and an uuid HtmlRouteProvider which can directly be used in entity type definitions e.g. for uuid based canonical path.
The long term target is still to get more uuid possibilities in core but I think the chance grows if we get things running in contrib world.