Remove libvlc hack, and fixes missing input state changes

- Run the volume/mute handling on the COM thread,
  removes remaining volume hacks.
- Spawn session manager from device rather than client (fixes #7809)
- Insulate session management from output API (refs #7394)

A library should not call exit(), but I do not see any easy way around
it: if libvlc_new() returns NULL on error so real errors cannot be
distinguished from --help stuff. Also --daemon already calls exit()
(through daemon()).

This introduces an O(1) memory leak when calling --help. It could be
fixed by merging libvlc_InternalCreate() and libvlc_InternalInit().

(If daemonizing succeeded, daemon() will call exit(0) internally.)

This seemed like a good idea to support xdg-screensaver. But it really
goes in the way.

This is required to remove the dependency on the window provider.

This reverts commit 0330378c.
This reverts commit 0f233f49.

Init() already initializes the aspect ratio, and does it correctly
(unlike these two commits) with video_format_ScaleCropAr().

The default output plugin is file for obvious backward compatibility
reasons. Note that using anything but the file output really only makes
sense for MPEG-TS streams.

Remove duplicate option

There is no need to reinitialize the structure.

The D-Bus interface is always started automatically. It should NOT be
added to --control.

...instead of libvlc.c. Note that this only concerns the playlist SD.
The LibVLC SD were always dealt with separately.

Those interfaces that need playlist deactivation can now call it
explicitly.