New condition/action entry 'category' for 'display-buffer' (bug#69983)

New condition/action entry 'category' for 'display-buffer' (bug#69983)

* doc/lispref/windows.texi (Choosing Window): Provide an example
of using '(category . comint)' in the condition of 'display-buffer-alist'
and in the action of 'display-buffer'.
(Buffer Display Action Alists): Add a new action alist entry 'category'.

* lisp/subr.el (buffer-match-p): Add a new condition 'category'.

* lisp/window.el (display-buffer): Document a new action alist entry
'category'.

(cherry picked from commit 9af533dc751e5220a545ca7e15456992cbbfab98)