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'.

lisp/faces.el

@@ -2738,6 +2738,33 @@ Note: Other faces cannot inherit from the cursor face."
   :version "21.1"
   :group 'basic-faces)
 
+(defface tab-bar
+  '((((class color) (min-colors 88))
+     :inherit variable-pitch
+     :background "grey85"
+     :foreground "black")
+    (((class mono))
+     :background "grey")
+    (t
+     :inverse-video t))
+  "Tab bar face."
+  :version "27.1"
+  :group 'basic-faces)
+
+(defface tab-line
+  '((((class color) (min-colors 88))
+     :inherit variable-pitch
+     :height 0.9
+     :background "grey85"
+     :foreground "black")
+    (((class mono))
+     :background "grey")
+    (t
+     :inverse-video t))
+  "Tab line face."
+  :version "27.1"
+  :group 'basic-faces)
+
 (defface menu
   '((((type tty))
      :inverse-video t)

lisp/tab-bar.el

@@ -44,25 +44,12 @@
   :group 'convenience
   :version "27.1")
 
-(defgroup tab-bar-faces nil
+(defgroup tab-bar-faces '((tab-bar custom-face)) ; tab-bar is defined in faces.el
   "Faces used in the tab bar."
   :group 'tab-bar
   :group 'faces
   :version "27.1")
 
-(defface tab-bar
-  '((((class color) (min-colors 88))
-     :inherit variable-pitch
-     :background "grey85"
-     :foreground "black")
-    (((class mono))
-     :background "grey")
-    (t
-     :inverse-video t))
-  "Tab bar face."
-  :version "27.1"
-  :group 'tab-bar-faces)
-
 (defface tab-bar-tab
   '((default
       :inherit tab-bar)

lisp/tab-line.el

@@ -35,26 +35,12 @@
   :group 'convenience
   :version "27.1")
 
-(defgroup tab-line-faces nil
+(defgroup tab-line-faces '((tab-line custom-face)) ; tab-line is defined in faces.el
   "Faces used in the tab line."
   :group 'tab-line
   :group 'faces
   :version "27.1")
 
-(defface tab-line
-  '((((class color) (min-colors 88))
-     :inherit variable-pitch
-     :height 0.9
-     :background "grey85"
-     :foreground "black")
-    (((class mono))
-     :background "grey")
-    (t
-     :inverse-video t))
-  "Tab line face."
-  :version "27.1"
-  :group 'tab-line-faces)
-
 (defface tab-line-tab
   '((default
       :inherit tab-line)