Misc: Use TODO() consistently in implementation stubs

#KT-13589 Fixed

idea/idea-completion/testData/handlers/basic/override/AfterValKeyword.kt.after

@@ -4,7 +4,7 @@ interface I {
 
 class A : I {
     override val someVal: String?
-        get() = <caret><selection>throw UnsupportedOperationException()</selection>
+        get() = <caret><selection>TODO("not implemented")</selection> //To change initializer of created properties use File | Settings | File Templates.
 }
 
 // ELEMENT_TEXT: "override val someVal: String?"

idea/idea-completion/testData/handlers/basic/override/ImplementVal.kt.after

@@ -4,7 +4,7 @@ interface I {
 
 class A : I {
     override val someVal: String?
-        get() = <caret><selection>throw UnsupportedOperationException()</selection>
+        get() = <caret><selection>TODO("not implemented")</selection> //To change initializer of created properties use File | Settings | File Templates.
 }
 
 // ELEMENT_TEXT: "override val someVal: String?"

idea/idea-completion/testData/handlers/basic/override/ImplementVar.kt.after

@@ -4,7 +4,7 @@ interface I {
 
 class A : I {
     override var someVar: String
-        get() = <caret><selection>throw UnsupportedOperationException()</selection>
+        get() = <caret><selection>TODO("not implemented")</selection> //To change initializer of created properties use File | Settings | File Templates.
         set(value) {
         }
 }