Migrate relaxation scripts from `BatchRelaxer` to `TorchSim`

[zdcao121]

BatchRelaxer is no longer maintained. It would be better to replace it with TorchSim, which is faster and better supported. Orb v0.6 also integrates well with torch-sim, which should simplify migration. For details on how to use TorchSim with Orb, please refer to the Orb documentation.

TODO:

• replace BatchRelaxer withTorchSim in mlff_relax_batch.py