Change representation of extension functions

idea/testData/completion/basic/ExtensionFromStandardLibrary.kt

@@ -9,6 +9,6 @@ fun firstFun() {
 
 // RUNTIME: 1
 // TIME: 1
-// EXIST: toLinkedList~() in kotlin
-// EXIST: toLinkedList~() in kotlin.nullable
+// EXIST: toLinkedList@toLinkedList()~for java.lang.Iterable<T> in kotlin
+// EXIST: toLinkedList@toLinkedList()~for T? in kotlin.nullable
 // NUMBER: 2

idea/testData/completion/basic/FunctionCompletionFormatting.kt

@@ -4,4 +4,4 @@ fun some() {
     tes<caret>
 }
 
-// EXIST: test~(a : jet.Int)
+// EXIST: test@test(a : jet.Int)