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

#KT-11799 Fixed

idea/testData/quickfix/createFromUsage/createFunction/binaryOperations/plusOnLibType.kt.after

@@ -7,6 +7,6 @@ fun test() {
     val a: A<Int> = 2 + A(1)
 }
 
-infix operator fun Int.plus(a: A<Int>): A<Int> {
+private infix operator fun Int.plus(a: A<Int>): A<Int> {
     TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }

idea/testData/quickfix/createFromUsage/createFunction/binaryOperations/quotedName.kt.after

@@ -5,6 +5,6 @@ fun test() {
     val t: Int = 1 `!u00A0` 2
 }
 
-infix fun Int.`!u00A0`(i: Int): Int {
+private infix fun Int.`!u00A0`(i: Int): Int {
     TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }