[KLIB] Mark DFG serialization code as unused and planned for removal

^KT-66218

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/serializeModuleIntoKlib.kt

@@ -63,7 +63,7 @@ class KotlinFileSerializedData private constructor(
 class SerializerOutput<Dependency : KotlinLibrary>(
     val serializedMetadata: SerializedMetadata?,
     val serializedIr: SerializedIrModule?,
-    val dataFlowGraph: ByteArray?,
+    val dataFlowGraph: ByteArray?, // TODO (KT-66218): remove this property
     val neededLibraries: List<Dependency>,
 )
 

compiler/util-klib/src/org/jetbrains/kotlin/library/impl/KotlinLibraryWriterImpl.kt

@@ -116,7 +116,7 @@ fun buildKotlinLibrary(
     nopack: Boolean,
     perFile: Boolean,
     manifestProperties: Properties?,
-    dataFlowGraph: ByteArray?,
+    dataFlowGraph: ByteArray?, // TODO (KT-66218): remove this property
     builtInsPlatform: BuiltInsPlatform,
     nativeTargets: List<String> = emptyList()
 ): KotlinLibraryLayout {

native/utils/src/org/jetbrains/kotlin/konan/library/impl/KonanLibraryWriterImpl.kt

@@ -54,7 +54,7 @@ fun buildLibrary(
     nopack: Boolean,
     shortName: String?,
     manifestProperties: Properties?,
-    dataFlowGraph: ByteArray?
+    dataFlowGraph: ByteArray? // TODO (KT-66218): remove this property
 ): KonanLibraryLayout {
 
     val libFile = File(output)