[IRBuilder] CreateIntrinsic with implicit mangling

Add a new IRBuilderBase::CreateIntrinsic which takes the return type and
argument values for the intrinsic call but does not take an explicit
list of types to mangle. Instead the builder works this out from the
intrinsic declaration and the types of the supplied arguments.

This means that the mangling is hidden from the client, which in turn
means that intrinsic definitions can change which arguments are mangled
without requiring any changes to the client code.

Differential Revision: https://reviews.llvm.org/D130776