This commit includes the basic Java stubs generation infrastructure and
the corresponding tests. The main entry point is called
Kapt4StubGenerator. Calls to it from production code will be added in a
separate commit.
#KT-51982
All of these have a different order of declarations and/or extra
`@NotNull` annotations on fields, both of which doesn't seem like a
problem.
#KT-49682
Pavel Mikhailovskii