Specify a custom location for `MUJOCO_LOG.TXT`

[ethanmusser]

Is your feature request related to a problem? Please describe. The MuJoCo log is always written to the MUJOCO_LOG.TXT file in the calling directory, which is not ideal for all project structures.

Describe the solution you'd like

• Specify a custom directory in which MUJOCO_LOG.TXT is generated.
• Specify a custom filename for the MuJoCo log.

Describe alternatives you've considered

• Moving the file after program execution is completed (cumbersome and feels like a hack).

Additional context N/A