Officially deprecate skin autodiscovery

Corresponding change in REL1_23 (different, because core skins still use
autodiscovery in that version): If9125ef587ce11f0d69f12eacd00ae7236139798.

Bug: 65748
Change-Id: I6fc30f97d4b35820c132c4892abf6d2c86f9482e