[K2] Revert commit Pass FirFile to metadata serialization

We will ignore this for now. It is quite painful to bring `FirFile`
in all necessary places.

#KT-57812

compiler/incremental-compilation-impl/src/org/jetbrains/kotlin/incremental/incrementalFirCacheUtils.kt

@@ -46,7 +46,6 @@ internal fun collectNewDirtySources(
                     body: (MetadataSerializer) -> Unit
                 ) {
                     val serializer = makeLocalFirMetadataSerializerForMetadataSource(
-                        it,
                         metadata,
                         analyzedOutput.session,
                         analyzedOutput.scopeSession,
@@ -74,7 +73,7 @@ internal fun collectNewDirtySources(
                 }
 
                 override fun visitFile(file: FirFile, data: MutableList<MetadataSerializer>) {
-                    val metadata = FirMetadataSource.File(file)
+                    val metadata = FirMetadataSource.File(listOf(file))
                     withMetadataSerializer(metadata, data) {
                         file.acceptChildren(this, data)
                         // TODO: compare package fragments?