In the playbackbox, allow jumping to an episode's display group.

Provides keybindings and a menu entry such that if you've highlighted
an episode in the All Programs view, you can see that episode
highlighted within its title's display group.  For example, you see
that a new episode has recorded, and you can quickly jump to the
episode's display group to see if there are any other episodes you
should catch up on first.

Thanks to Angela Schmid for the patch.

Fixes #12157

Signed-off-by: Jim Stichnoth <jstichnoth@mythtv.org>