1) Add Java use sites which are similar to Kotlin use sites;
2) Use the new test format: separated Java and Kotlin sources (Java declarations + use sites and Kotlin corresponding use sites), Java declarations + use sites will be a sharable test suite;
3) Remove any dependencies from Java sources except `Object` and jspecify annotations;
4) Introduce a new test runner which compiles Java and Kotlin sources together and dumps all descriptors.
