Video recorder: distinguish input and output fps (#1817)
Video recorder: distinguish input and output fps (#1817)

* Video recorder: distinguish input and output fps

Common video players such as VLC, or Quicktime struggle to play videos
with low framerate, which is problematic for environments where the
policy
frequency is low (e.g. 1 Hz).
See: https://superuser.com/a/601916

This commit sets:
- The input image sequence framerate to the metadata
'video.frames_per_second'
- The output video framerate to at least 30 fps

* Use a configurable output video framerate

This output video framerate is different from the image sequence
framerate:
- when the environment fps is low, the output video fps can be increased
so that players like VLC or Quicktime handle them more gracefully (they
struggle at low fps)
- when the environment fps is very high, the output video can still be
recorded at a lower fps to better compression.

It is configured through the 'video.output_frames_per_second' metadata
and defaults to 'video.frames_per_second' (which itself defaults to 30)

Farama-Foundation/Gymnasium,Farama-Foundation/Gymnasium