Update torchbench commit pin, add sam_fast benchmark (#121420)
After this, the sam_fast benchmark can now be run in the pytorch repo:
```
SEGMENT_ANYTHING_FAST_USE_FLASH_4=0 benchmarks/dynamo/torchbench.py --inference --amp --performance --backend=inductor --explain --only sam_fast
```
sam_fast is designed for inference only, with cuda and amp on. The code adds these restrictions to the benchmark.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121420
Approved by: https://github.com/oulgen, https://github.com/msaroufim
