[BE] Use `DispatchKeySet` in `check_base_legacy_new` (#65535)
Summary:
Refactor:
```
TORCH_CHECK ( key == a ||
key == b ||
key == c,
"expected key to be in ", a, " or ", b , " or ", c,
" but got ", key);
```
into
```
TORCH_CHECK( key_set.has(key),
"expected key to be in ", key_set,
" but got ", key );
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65535
Reviewed By: wconstab
Differential Revision: D31144239
Pulled By: malfet
fbshipit-source-id: 68a053041a38f043e688e491889dd7ee258f3db3
