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

js/js.serializer/src/org/jetbrains/kotlin/serialization/js/jsProtoBufUtil.kt

@@ -1,31 +0,0 @@
-/*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.serialization.js
-
-import org.jetbrains.kotlin.serialization.ProtoBuf
-import java.io.ByteArrayInputStream
-
-public fun ByteArray.toPackageProto(): ProtoBuf.Package {
-    val registry = KotlinJavascriptSerializedResourcePaths.extensionRegistry
-    return ProtoBuf.Package.parseFrom(ByteArrayInputStream(this), registry)!!
-}
-
-public fun ByteArray.toClassProto(): ProtoBuf.Class {
-    val registry = KotlinJavascriptSerializedResourcePaths.extensionRegistry
-    return ProtoBuf.Class.parseFrom(ByteArrayInputStream(this), registry)
-}
-