FIR2IR: Refine definition if we need a fake override

`realDeclarationSymbols` that was used before is built from klass.declarations that doesn't
contain e.g. declarations from enhancement
Next time, we should get rid of `realDeclarationSymbols` and use only
originalDeclaration.origin.fromSupertypes, but originalSymbol.callableId.classId == classId
doesn't work correctly

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/FakeOverrideGenerator.kt

@@ -143,11 +143,13 @@ class FakeOverrideGenerator(
         scope: FirTypeScope,
     ) where S : FirCallableSymbol<D>, S : PossiblyFirFakeOverrideSymbol<D, S> {
         if (originalSymbol !is S || originalSymbol in realDeclarationSymbols) return
-
+        val classId = klass.symbol.classId
         val originalDeclaration = originalSymbol.fir
+        if (originalSymbol.callableId.classId == classId && !originalDeclaration.origin.fromSupertypes) return
+
         val origin = IrDeclarationOrigin.FAKE_OVERRIDE
         val baseSymbol = originalSymbol.deepestOverriddenSymbol() as S
-        val classId = klass.symbol.classId
+
         if ((originalSymbol.isFakeOverride || originalSymbol.isIntersectionOverride) &&
             originalSymbol.callableId.classId == classId
         ) {

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

@@ -5,19 +5,19 @@
 
 package org.jetbrains.kotlin.fir.declarations
 
-sealed class FirDeclarationOrigin {
+sealed class FirDeclarationOrigin(val fromSupertypes: Boolean = false) {
     object Source : FirDeclarationOrigin()
     object Library : FirDeclarationOrigin()
     object Java : FirDeclarationOrigin()
     object Synthetic : FirDeclarationOrigin()
     object SamConstructor : FirDeclarationOrigin()
-    object FakeOverride : FirDeclarationOrigin()
+    object FakeOverride : FirDeclarationOrigin(fromSupertypes = true)
     object Enhancement : FirDeclarationOrigin()
     object ImportedFromObject : FirDeclarationOrigin()
-    object IntersectionOverride : FirDeclarationOrigin()
+    object IntersectionOverride : FirDeclarationOrigin(fromSupertypes = true)
     object Delegated : FirDeclarationOrigin()
 
     class Plugin(val key: FirPluginKey) : FirDeclarationOrigin()
 }
 
-abstract class FirPluginKey
+abstract class FirPluginKey