Show admin bar in backend by default

[dimadin]

With removal of favorites menu, there are no quick links in the backend that are shown by default.

I propose that we change current behavior and to show admin bar everywhere by default.

(when I say by default, it means for new users and users registered before 3.2 that haven't updated their profile)

[nacin]

We were just talking about this yesterday, and there might even be an existing ticket for this. The core team is on board for this, for 3.3.

[ryan]

In [18451]:

Show admin bar in single site backend by default. Props dimadin. fixes #17899