* lisp/tab-bar.el: New faces and face options.

* lisp/tab-bar.el: New faces and face options.

* lisp/tab-bar.el (tab-bar-tab-group-current)
(tab-bar-tab-group-inactive, tab-bar-tab-ungrouped): New deffaces.
(tab-bar-tab-face-function): New defcustom.
(tab-bar-tab-face-default): New function.
(tab-bar-tab-name-format-default): Use it.
(tab-bar-tab-group-format-default): Use tab-bar-tab-group-inactive face.
(tab-bar-tab-group-face-function): New defcustom.
(tab-bar-tab-group-face-default): New function.
(tab-bar--format-tab-group): Add new arg 'current-p'.
(tab-bar-format-tabs-groups): Prepend current group name before first tab.
Override tab-bar-tab-face-function with tab-bar-tab-group-face-function.