[FIR2IR] Automatically store IR declaration in its parent upon creation

Previously, creating a declaration with Fir2IrCallableDeclarationsGenerator/
  Fir2IrClassifiersGenerator didn't guarantee that this declaration will
  be actually added to the list of parent class/file declarations, which
  lead to situations when FIR2IR created some declarations in the air
  (mostly fake-overrides)

compiler/testData/ir/irText/classes/delegatedImplementationOfJavaInterface.fir.kt.txt

@@ -5,6 +5,10 @@ class Test : J {
 
   }
 
+  private val j: J
+    field = j
+    private get
+
   override fun takeNotNull(@NotNull x: @EnhancedNullability String) {
     <this>.#j.takeNotNull(x = x)
   }
@@ -31,8 +35,5 @@ class Test : J {
     return <this>.#j.returnsFlexible()
   }
 
-  private val j: J
-    field = j
-    private get
-
 }
+