[dtensor][2/n] use op overload instead of function schema (#107306)
function schema doesn't provide us anything as we can also get the schema from `op._schema`, include the op directly in op_schema makes easier for sharding prop to do fake execution, and in principle it should also make the hash comparison faster as we don't need to hash the function schema, instead we just hash the `id(op)` which is constant
This PR is just a refactor to include op to OpSchema instead of func schema, no other logic changes
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107306
Approved by: https://github.com/fduwjj
