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

#KT-11799 Fixed

idea/testData/quickfix/createFromUsage/createFunction/call/extensionByExtensionReceiver/extensionFunction.kt.after

@@ -9,6 +9,6 @@ fun A.test() {
     bar(foo(n))
 }
 
-fun A.foo(n: Int): Boolean {
+private fun A.foo(n: Int): Boolean {
     TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }

idea/testData/quickfix/createFromUsage/createFunction/call/extensionByExtensionReceiver/extensionLambda.kt.after

@@ -12,6 +12,6 @@ fun test() {
     }
 }
 
-fun A.foo(n: Int): Boolean {
+private fun A.foo(n: Int): Boolean {
     TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
 }

idea/testData/quickfix/createFromUsage/createFunction/call/extensionByExtensionReceiver/extensionPropertyGetter.kt.after

@@ -2,7 +2,7 @@
 // ERROR: Property must be initialized
 class A(val n: Int)
 
-val A.foo: Boolean<caret>
+private val A.foo: Boolean
 
 class B {
     val A.test: Boolean get() = foo

idea/testData/quickfix/createFromUsage/createFunction/call/extensionByExtensionReceiver/extensionPropertySetter.kt.after

@@ -2,7 +2,7 @@
 // ERROR: Property must be initialized
 class A(val n: Int)
 
-var A.foo: Boolean<caret>
+private var A.foo: Boolean
 
 class B {
     var A.test: Boolean