[mlir] Add an interface for Cast-Like operations

A cast-like operation is one that converts from a set of input types to a set of output types. The arity of the inputs may be from 0-N, whereas the arity of the outputs may be anything from 1-N. Cast-like operations are removable in cases where they produce a "no-op", i.e when the input types and output types match 1-1.

Differential Revision: https://reviews.llvm.org/D94831