[MPS] Implement MPSGenerator to enable manual random seeding (#91348)
This patch adds support for creating torch.Generator for MPS device, and enables its functions such as manual_seed, get_state, and set_state.
Fixes #84288 and #84516
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91348
Approved by: https://github.com/malfet, https://github.com/albanD
