[FIR] Introduce & use FirDelegatedMemberScope

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/FirDeclarationOrigin.kt

@@ -15,6 +15,7 @@ sealed class FirDeclarationOrigin {
     object Enhancement : FirDeclarationOrigin()
     object ImportedFromObject : FirDeclarationOrigin()
     object IntersectionOverride : FirDeclarationOrigin()
+    object Delegated : FirDeclarationOrigin()
 
     class Plugin(val key: FirPluginKey) : FirDeclarationOrigin()
 }