JS: serialize .kjsm package-wise, adapt decompiler & stub builder

Instead of multiple .kjsm files for different classes and .kotlin_string_table,
.kotlin_file_table, .kotlin_classes files for each package, serialize the
contents of each package to a single foo/bar/baz/baz.kjsm file. The short name
of the file is the last segment in the FQ name of the package, or
"root-package" if the package is root.

There are two main reasons for this change:
1) Such structure takes less space, is more IO-friendly and will not cause
   multiple exceptions as the old one, where we sometimes tried to read
   non-existing files
2) This is exactly the same format that is used to serialize built-in
   declarations (.kotlin_builtins) at the moment, which will allow us to reuse
   some code

Also write a separate Header protobuf message to the beginning of the .kjsm
file. This will be used as arguments of the kotlin.Metadata annotation are used
in the JVM-specific parts of the compiler: to be able to provide some general
information about the binary file without parsing the whole protobuf data.

This commit breaks decompiled text & stub builder consistency tests. This is OK
because they're removed in a future commit.

Fixes EA-79605, EA-81947, EA-84277 and maybe EA-86787

 #KT-10894 Fixed
 #KT-14124 Fixed
 #KT-15755 Fixed

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/NameResolverImpl.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.serialization.ProtoBuf
 import org.jetbrains.kotlin.serialization.ProtoBuf.QualifiedNameTable.QualifiedName
-import java.io.InputStream
 import java.util.*
 
 class NameResolverImpl(
@@ -29,7 +28,7 @@ class NameResolverImpl(
         private val qualifiedNames: ProtoBuf.QualifiedNameTable
 ) : NameResolver {
 
-    override fun getString(index: Int) = strings.getString(index)
+    override fun getString(index: Int): String = strings.getString(index)
 
     override fun getName(index: Int) = Name.guessByFirstCharacter(strings.getString(index))
 
@@ -65,12 +64,4 @@ class NameResolverImpl(
         }
         return Triple(packageNameSegments, relativeClassNameSegments, local)
     }
-
-    companion object {
-        fun read(stream: InputStream): NameResolverImpl {
-            val simpleNames = ProtoBuf.StringTable.parseDelimitedFrom(stream)
-            val qualifiedNames = ProtoBuf.QualifiedNameTable.parseDelimitedFrom(stream)
-            return NameResolverImpl(simpleNames, qualifiedNames)
-        }
-    }
 }