Add MPD stats viewer to 'mpc' (Bug#76350)

Add MPD stats viewer to 'mpc' (Bug#76350)

* lisp/mpc.el (mpc-server-stats): New command.
(mpc-mode-menu): Add menu item.
(mpc--server-stats-date, mpc--server-stats-duration):
New variable.
(mpc--server-stats-date, mpc--server-stats-duration):
(mpc--server-stats-format): New function.
(mpc-song-viewer-value, mpc-song-viewer-tag):
(mpc-song-viewer-empty): Remove face.
(mpc-table-value, mpc-table-key, mpc-table-empty): New face.
(mpc-describe-song): Use new table face names.

(cherry picked from commit df93e53a1c648654d8b128a5955bb4ff0229b041)