Interop Atom's members test should return inherited members as well

[hubertp]

Follow up on #6275 (comment).

We currently report members defined on the Atom itself but not the ones inherited, like from e.g. Any. Since those are also invokable they should be reported as well.

[JaroslavTulach]

There is Meta.get_type_methods method and it should probably be consistent with Atom.getMembers. We should use ValuesGenerator and write a test to verify the behavior is consistent for Atom as well as for instances of Enso builtin types. We cannot influence getMembers behavior of non-Enso objects, so the test shall not check them.