Remove StringTable.serializeTo, add JvmProtoBufUtil.writeData

StringTable.serializeTo was effectively only used for JvmStringTable,
but was declared in StringTable because of the usage in
DescriptorSerializer.serialize (which, in turn, was only used from JVM
codegen)

core/metadata/src/org/jetbrains/kotlin/metadata/serialization/StringTable.kt

@@ -5,8 +5,6 @@
 
 package org.jetbrains.kotlin.metadata.serialization
 
-import java.io.OutputStream
-
 interface StringTable {
     fun getStringIndex(string: String): Int
 
@@ -14,6 +12,4 @@ interface StringTable {
      * @param className the fully qualified name of some class in the format: `org/foo/bar/Test.Inner`
      */
     fun getQualifiedClassNameIndex(className: String, isLocal: Boolean): Int
-
-    fun serializeTo(output: OutputStream)
 }