Move tab-bar and tab-line faces to faces.el (part of bug#41200)

Move tab-bar and tab-line faces to faces.el (part of bug#41200)

These are basic faces, so they need to be defined in
faces.el, otherwise (get 'tab-line 'face) returns 0.

* lisp/faces.el (tab-bar, tab-line): Move faces here
from tab-bar.el and tab-line.el.

* lisp/tab-bar.el (tab-bar): Move face to faces.el.
(tab-bar-faces): Add '((tab-bar custom-face))
to the second arg MEMBERS of 'defgroup'.

* lisp/tab-line.el (tab-line): Move face to faces.el.
(tab-line-faces): Add '((tab-line custom-face))
to the second arg MEMBERS of 'defgroup'.