[ORC-RT] Add a WrapperFunctionCall utility.

WrapperFunctionCall represents a call to a wrapper function as a pair of a
target function (as an ExecutorAddr), and an argument buffer range (as an
ExecutorAddrRange). WrapperFunctionCall instances can be serialized via
SPS to send to remote machines (only the argument buffer address range is
copied, not any buffer content).

This utility will simplify the implementation of JITLinkMemoryManager
allocation actions in the ORC runtime.