FirProvider: search for fake overridden symbol containing file correctly

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirCallableSymbol.kt

@@ -11,4 +11,7 @@ import org.jetbrains.kotlin.fir.symbols.CallableId
 
 abstract class FirCallableSymbol<D : FirCallableDeclaration<D>> : AbstractFirBasedSymbol<D>() {
     abstract val callableId: CallableId
+
+    open val overriddenSymbol: FirCallableSymbol<D>?
+        get() = null
 }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -25,7 +25,7 @@ open class FirNamedFunctionSymbol(
     callableId: CallableId,
     val isFakeOverride: Boolean = false,
     // Actual for fake override only
-    val overriddenSymbol: FirNamedFunctionSymbol? = null
+    override val overriddenSymbol: FirNamedFunctionSymbol? = null
 ) : FirFunctionSymbol<FirNamedFunction>(callableId)
 
 class FirConstructorSymbol(

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirVariableSymbol.kt

@@ -22,7 +22,7 @@ open class FirPropertySymbol(
     callableId: CallableId,
     val isFakeOverride: Boolean = false,
     // Actual for fake override only
-    val overriddenSymbol: FirPropertySymbol? = null
+    override val overriddenSymbol: FirPropertySymbol? = null
 ) : FirVariableSymbol<FirProperty>(callableId)
 
 class FirBackingFieldSymbol(callableId: CallableId) : FirVariableSymbol<FirProperty>(callableId)