Create from Usage: Make extension functions/properties 'private' by default

#KT-11799 Fixed

idea/testData/quickfix/createFromUsage/createFunction/callableReferences/extensionWithReceiverInCallableRef.kt.after

@@ -8,6 +8,6 @@ fun test() {
     consume(1.map(Int::foo))
 }
 
-fun Int.foo(): String {
-    <selection>TODO("not implemented") //To change body of created functions use File | Settings | File Templates.</selection>
+private fun Int.foo(): String {
+    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }

idea/testData/quickfix/createFromUsage/createFunction/callableReferences/nonExtensionWithReceiverInCallableRef.kt.after

@@ -8,6 +8,6 @@ fun test() {
     consume(1.map(Int::foo))
 }
 
-fun Int.foo(): String {
-    <selection>TODO("not implemented") //To change body of created functions use File | Settings | File Templates.</selection>
+private fun Int.foo(): String {
+    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }