[mlir][arith] Define mulsi_extended op

Extend D139688 with the signed version of the extended multiplication
op. Add conversion to the SPIR-V and LLVM dialects.

This was originally proposed in:
https://discourse.llvm.org/t/rfc-arith-add-extended-multiplication-ops/66869.

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D139743