Option to synchronize video logging stream with physics thread

[mt-]

Issue:
The video framerate when using STATE_LOGGING_VIDEO_MP4 is independent of the physics engine timestep. This causes videos to record at a much higher framerate then the physics engine is running at.

Goal:
Synchronize the framerate of STATE_LOGGING_VIDEO_MP4 with the physics thread.

Relevant info from Erwin:
At the moment, the ffmpeg video stream is generated from the graphics thread, which runs asynchronously from the physics. It cannot be synchronized. We can add an option to force to synchronize them for this purpose...

See this question thread for more details:
https://pybullet.org/Bullet/phpBB3/viewtopic.php?f=24&t=11976