Refactored ConvertMemberToExtension to re-use original declaration instead of regenerating it by text

#KT-4920 Fixed

idea/testData/intentions/declarations/convertMemberToExtension/varWithDefaultSetter.kt

@@ -1,6 +1,6 @@
 // ERROR: Property must be initialized
 class Owner {
     var <caret>p: Int
-      get() = 1
-      set
+        get() = 1
+        set
 }