IR: extract & rename getTopLevelDeclaration() to IrLazyFunctionBase

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/AbstractFir2IrLazyFunction.kt

@@ -123,18 +123,10 @@ abstract class AbstractFir2IrLazyFunction<F : FirCallableDeclaration>(
     private fun tryLoadIr(): Boolean {
         if (!isInline || isFakeOverride) return false
         if (!extensions.irNeedsDeserialization) return false
-        val toplevel = getToplevel()
+        val toplevel = getTopLevelDeclaration()
         return (toplevel as? DeserializableClass)?.loadIr() ?: false
     }
 
-    private fun getToplevel(): IrDeclaration {
-        var current: IrDeclaration = this
-        while (current.parent !is IrPackageFragment) {
-            current = current.parent as IrDeclaration
-        }
-        return current
-    }
-
     companion object {
         private val JVM_STATIC_CLASS_ID = ClassId.topLevel(JVM_STATIC_ANNOTATION_FQ_NAME)
     }