[inductor] new way to compile f64 libdevice calls (#87189)
Porting over [torchdynamo/#1633](https://github.com/pytorch/torchdynamo/pull/1633)
`torch/_inductor/codegen/triton.py` now defines `libdevice_<function>` variants
of some functions. You can request dispatch to those for
float64 dtypes when using `register_pointwise` by setting
`use_libdevice_for_f64=True`.
Other minor changes:
- In triton, sigmoid now codegens tl.sigmoid
- silu now comes from decomp, not lowering
- Some test skips no longer necessary, removed or made xfails
Switching to `tl.sigmoid` has exactly same performance.
Moving `silu` to decomp does not change anything, same triton code is generated.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87189
Approved by: https://github.com/ngimel
