Decompile builtins (kotlin_class and kotlin_package files)

The main purpose of this is to be able to index builtin declarations and enable go to symbol/class functionality in ide
Also it makes sense to show builtin classes (Any, Int ...) as classes when browsing kotlin-runtime.jar

Refactor decompiler code to eliminate existing and potential duplication
Share the code between js (kjsm) decompilation and builtin decompilation heavily

idea/idea-test-framework/src/org/jetbrains/kotlin/idea/test/testUtils.kt

@@ -33,7 +33,7 @@ import org.jetbrains.kotlin.diagnostics.rendering.DefaultErrorMessages
 import org.jetbrains.kotlin.idea.caches.resolve.LibraryModificationTracker
 import org.jetbrains.kotlin.idea.caches.resolve.analyzeFullyAndGetResult
 import org.jetbrains.kotlin.idea.decompiler.KotlinDecompiledFileViewProvider
-import org.jetbrains.kotlin.idea.decompiler.classFile.KtClsFile
+import org.jetbrains.kotlin.idea.decompiler.KtDecompiledFile
 import org.jetbrains.kotlin.idea.references.BuiltInsReferenceResolver
 import org.jetbrains.kotlin.psi.KtFile
 import java.util.*
@@ -106,7 +106,7 @@ public fun unInvalidateBuiltinsAndStdLib(project: Project, runnable: RunnableWit
 
     builtInsSources.forEach { unInvalidateFile(it) }
     stdLibViewProviders.forEach {
-        it.allFiles.forEach { unInvalidateFile(it as KtClsFile) }
+        it.allFiles.forEach { unInvalidateFile(it as KtDecompiledFile) }
         vFileToViewProviderMap.set(it.virtualFile, it)
     }
 }