[FIR] Create fake hidden versions of List.getFirst/getLast in JDK < 21

... so that overrides are marked as deprecated regardless of the JDK.

#KT-65440 Fixed

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

@@ -35,6 +35,7 @@ sealed class FirDeclarationOrigin(
         object FakeFunction : Synthetic()
         object ForwardDeclaration : Synthetic()
         object ScriptTopLevelDestructuringDeclarationContainer : Synthetic()
+        object FakeHiddenInPreparationForNewJdk : Synthetic()
     }
     object DynamicScope : FirDeclarationOrigin()
     object SamConstructor : FirDeclarationOrigin()