Unify extension point and extension registration in plugin and cli
Minor: fix JetCoreEnvironment#(createForProduction, createForTests) call sites for JVM.
JS backend: added the support nativeInvoke, nativeGetter, nativeSetter.
Minor in JS backend: refactoring JsInvocation.
JsDescriptorUtils#(isExtension, isOverride, getContainingClass) -> DescriptorUtils#(*)
Move AnnotationsUtils to js.frontend
JS frontend: added checkers for nativeInvoke, nativeGetter, nativeSetter.
Move LibrarySourcesConfigWithCaching to js.frontend module.
Move JsUnitTestReporter.java to utils.
Drop platform parameter in diagnostic tests(partial revert of 2a334fc).
JS frontend: added tests for nativeInvoke, nativeGetter, nativeSetter.
Fix build on windows: use forward-slash in path to config files, it's important for access to files inside jar/zip.