[ORC] Add MethodWrapperHandler utility for WrapperFunction.

MethodWrapperHandler removes some of the boilerplate when writing wrapper
functions to wrap method calls. It can be used as a handler for wrapper
functions whose first argument is an ExecutorAddress: the address is cast to a
pointer of the given class type, then the given method function pointer is
called on that object pointer (passing the rest of the arguments).

E.g.

class MyClass {
public:
  void myMethod(uint32_t, bool) { ... }
};

// SPS Method signature for myMethod -- note MyClass object address as first
// argument.
using SPSMyMethodWrapperSignature =
  SPSTuple<SPSExecutorAddress, uint32_t, bool>;

// Wrapper function for myMethod.
WrapperFunctionResult
myMethodCallWrapper(const char *ArgData, size_t ArgSize) {
  return WrapperFunction<SPSMyMethodWrapperSignature>::handle(
     ArgData, ArgSize, makeMethodWrapperHandler(&MyClass::myMethod));
}