Convert member to extension: Support members of header/impl classes

#KT-18883 Fixed

idea/testData/multiModuleQuickFix/memberValToExtensionByHeader/js/js.kt

@@ -0,0 +1,3 @@
+impl class Foo {
+    impl val foo get() = 1
+}

idea/testData/multiModuleQuickFix/memberValToExtensionByHeader/js/js.kt.after

@@ -0,0 +1,4 @@
+impl class Foo {
+}
+
+impl val Foo.foo get() = 1