Improve perf for stage3 training (#18099)
### Improve perf for stage3 training - first wave
Port existing PythonOp/PythonOpGrad python runner to C++, also introduce
an unsafe run mode (to skip inplace, save for backward, materrialized
grad detection on the fly).
This reduce the overhead from XX~XXX us to X ~ lower end of XX us . In
LLAMA2 7B training with 8x32GV100, we have observed 6.7% gains over
PyTorch. (1.59 v.s. 1.49it/s)
Peak memory also dropped from 31GB to 28GB.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
