Adds `transform.func.cast_and_call` that takes a set of inputs and
outputs and replaces the uses of those outputs with a call to a function
at a specified insertion point.
The idea with this operation is to allow users to author independent IR
outside of a to-be-compiled module, and then match and replace a slice
of the program with a call to the external function.
Additionally adds a mechanism for populating a type converter with a set
of conversion materialization functions that allow insertion of
casts on the inputs/outputs to and from the types of the function
signature.
42b160356f