JS backend: fix get mangling name for generic methods with multiply upper bounds
JS backend: add getPackageName to BasicTest, checkBlackBox to SingleFileTranslationTest
JS backend: add NotNull and Nullable annotations
JS backend: improve test generator, support for backend header in test files
JS backend: add $backend=jvm for some tests for bridge methods
JS backend: add BridgeTestGenerated
JS backend: add javauitl.kt to bridges/_commonFiles
JS backend: add adapted tests for bridge methods from compiler/testData/codegen/box/bridges
JS backend: support for bridge methods