Add canonicalize pattern for aten.mul.int and aten.floordiv.int

[zezhang]

This PR add floordiv to the PY_BUILTIN_TO_TORCH_OP. For aten.mul.int and aten.floordiv.int ops, we add new Canonicalization Patterns as follow:

%1 = torch.aten.mul.int %input, %const-5
%2 = torch.aten.mul.int %1, %const-6

Will be replaced by

torch.aten.mul.int %input, %const-30

And

%1 = torch.aten.mul.int %input, %const-5
%2 = torch.aten.floordiv.int %1, %const-5

Will directly return %input

This PR also relaxes the float type constraint in TorchToTosa for the AtenRsubScalarOp conversion.

To test:

cmake --build build --target check-torch-mlir-all

[sjain-stanford]

LGTM