Sync the GPU thread on list/draw sync

[unknownbrackets]

Otherwise, the CPU gets ahead (inside the frame) and games get confused. I don't think there's any good workaround to avoid this, at least I can't think of one.

Fixes the FPS drops in most games (since they ended up waiting until the end of the frame and thought they were behind.) Hurts performance too, of course, but it's still better than with the thread disabled.

-[Unknown]

[unknownbrackets]

Also, very curious whether this can possibly improve the Virtua Tennis issue.

-[Unknown]

[hrydgard]

I wonder if we can make this more detailed, so that listsync only catches up to the mentioned display list and not all of them if there are several queued - or if I'm just misunderstanding something. Anyway, that's for later I guess.

[unknownbrackets]

Yeah, potentially we could do that for listsync. That's not a bad idea.

-[Unknown]

[hrydgard]

This, curiously, does not fix Virtua Tennis.

[solarmystic]

This addresses a few of the games in #3116 but have made others even worse, if that was possible

(e.g. Monster Hunter Freedom Unite's opening FMV plays fine at 30 FPS now, but the in game internal FPS has declined even further to the teens (12.9 FPS) and the screen now flickers intermittently.)

Further details in that linked thread.

[unknownbrackets]

Ended up not being worth it. Having the condition variable wake every time an event is consumed hurt more than the gain of ending listsync early.

-[Unknown]