Quick fix for SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE (#858)

* Quick fix for SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE
Fixes #KT-11876

* Revert accidental change

* Remove period

* ConvertExtensionToFunctionTypeFix: more tests

idea/testData/quickfix/superTypeIsExtensionType/typeWith1Argument.kt

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String, String) -> Unit'" "true"
+
+class Foo : <caret>String.(String) -> Unit {
+    override fun invoke(p1: String, p2: String) {
+    }
+}

idea/testData/quickfix/superTypeIsExtensionType/typeWith1Argument.kt.after

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String, String) -> Unit'" "true"
+
+class Foo : <caret>(String, String) -> Unit {
+    override fun invoke(p1: String, p2: String) {
+    }
+}

idea/testData/quickfix/superTypeIsExtensionType/typeWithNoArgument.kt

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String) -> Unit'" "true"
+
+class Foo : <caret>String.() -> Unit {
+    override fun invoke(p1: String) {
+    }
+}

idea/testData/quickfix/superTypeIsExtensionType/typeWithNoArgument.kt.after

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String) -> Unit'" "true"
+
+class Foo : <caret>(String) -> Unit {
+    override fun invoke(p1: String) {
+    }
+}

idea/testData/quickfix/superTypeIsExtensionType/typeWithTypeArgument.kt

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String, T) -> Unit'" "true"
+
+class Foo<T> : <caret>String.(T) -> Unit {
+    override fun invoke(p1: String, p2: T) {
+    }
+}

idea/testData/quickfix/superTypeIsExtensionType/typeWithTypeArgument.kt.after

@@ -0,0 +1,6 @@
+// "Convert supertype to '(String, T) -> Unit'" "true"
+
+class Foo<T> : <caret>(String, T) -> Unit {
+    override fun invoke(p1: String, p2: T) {
+    }
+}