[MPS][BE] Add native lerp support (#119036)
By implementing `out = self + weight * (end-self)` as MPS graph
LERP is tested by `test_output_match_lerp_cpu_float[32|16]` based on OpInfo and 10+ tests from `test_optim.py`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119036
Approved by: https://github.com/albanD
