TODOs for MethodHandleResolver

The work for supporting OpenJDK MethodHandles (JSR292) in OpenJ9 is ongoing. Below is the list of TODOs for the MethodHandleResolver class:

[ ] (1) Investigate if an equivalent for lookup.accessCheckArgRetTypes is needed for OpenJDK MH.
[ ] (2) In resolveInvokeDynamic, result[0] either stores a MemberName or Throwable. This leads to a type check in the interpreter or the object stored in result[0]. Investigate if the Throwable can be wrapped in a MemberName. This will help prevent type checks in the interpreter since result[0] will always be a MemberName. This will improve performance.
[ ] (3) Validate if new MethodHandles.Lookup(Class<?>) (OpenJDK) is equivalent to new MethodHandles.Lookup(Class<?>, boolean) (OpenJ9) once test builds are enabled.
[ ] (4) Validate if Lookup.IMPL_LOOKUP.revealDirect(bsm).getName() (OpenJDK) behaves similar to MethodHandle.getMethodName() (OpenJ9) once test builds are enabled.
[ ] (5) Investigate if MethodHandleNatives.linkMethodHandleConstant (in OpenJDK) is an alternative for sendResolveMethodHandle (in OpenJ9). If so, use MethodHandleNatives.linkMethodHandleConstant for OpenJDK MethodHandles since it accounts for all the error checking. Then, we won't need to find an alternative for lookup.accessCheckArgRetTypes.
[ ] (6) In https://github.com/eclipse/openj9/pull/11371, MethodHandleResolver.sendResolveMethodHandle starts using MethodHandleNatives.linkMethodHandleConstant in order to resolve OJDK MHs. As per https://github.com/eclipse/openj9/pull/11371#issuecomment-749747332, it is tentatively believed that Lookup.accessCheckArgRetTypes == VerifyAccess.isMemberAccessible. Due to lack of a test case, we were unable to concretely prove this relationship. During functional testing, any missing IllegalAccessErrors may be due to Lookup.accessCheckArgRetTypes != VerifyAccess.isMemberAccessible. If such a case arises, then the appropriate access check should be added after deriving the access check location from the RI.

eclipse-openj9 / openj9

TODOs for MethodHandleResolver #10913