[mlir][TableGen] Support intrinsics with multiple returns and overloaded operands.

For intrinsics with multiple returns where one or more operands are overloaded, the overloaded type is inferred from the corresponding field of the resulting struct, instead of accessing the result directly.

As such, the hasResult parameter of LLVM_IntrOpBase (and derived classes) is replaced with numResults. TableGen for intrinsics also updated to populate this field with the total number of results.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D91680