Extend benchmark with mujoco v4 envs

[MischaPanch]

Contact forces have been removed from obs going from v3 to v4, making the envs more challenging.

V4 is the new default in all our scripts, we should include benchmark results.

Generally, we should have a single script per example subdir that runs all experiments a la rliable and creates the benchmark files.

@opcode81 this is one argument in favor of inlcuding num_experiments=1 into all high level example scripts. It should be completely clear how the reported benchmark results were created, and in fact we should run the creation at least at every release.

I can look for compute sponsors :)