Revert "Support common metadata in kotlinx-metadata"

This reverts commit f9cc443e4f.

core/metadata/src/org/jetbrains/kotlin/metadata/builtins/readPackageFragment.kt

@@ -1,22 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.metadata.builtins
-
-import org.jetbrains.kotlin.metadata.ProtoBuf
-import org.jetbrains.kotlin.protobuf.ExtensionRegistryLite
-import java.io.InputStream
-
-fun InputStream.readBuiltinsPackageFragment(): Pair<ProtoBuf.PackageFragment?, BuiltInsBinaryVersion> =
-    use { stream ->
-        val version = BuiltInsBinaryVersion.readFrom(stream)
-        val proto =
-            if (version.isCompatible()) ProtoBuf.PackageFragment.parseFrom(
-                stream,
-                ExtensionRegistryLite.newInstance().apply(BuiltInsProtoBuf::registerAllExtensions)
-            )
-            else null
-        proto to version
-    }