LibVLC: media_player Possible deadlocks when using external locks

cf. discussion with @alexandre-janniaux here: !4915 (comment 426084)

!4915 (closed) is not introducing the issue, we already have few events that are sent directly from `vlc_player` functions. In that case, there will be an issue when:

1. libvlc application hold its own lock
2. libvlc application calls a libvlc_media_player function
3. It trigger an send directly or indirectly from that function
4. libvlc application try to hold its own lock from the callback
 => DEADLOCK

Here is a possible to way this behavior:

1. Some events can be moved from the vlc_player to the input_thread thread.
2. Few events (not related to input_thread can be sent to the destructor thread (that need to be renamed) to be sent asynchronously
3. Some input_thread are sent synchronously (cf. input_SetEsCatDelay) => All controls should be executed from the Mainloop