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

#KT-18883 Fixed

idea/testData/multiModuleQuickFix/memberValToExtensionByHeaderWithInapplicableImpl/header/header.kt

@@ -0,0 +1,9 @@
+// "Convert member to extension" "false"
+// ACTION: Convert property to function
+// ACTION: Introduce backing property
+// ACTION: Move to companion object
+// ACTION: Move to constructor
+
+header class Foo {
+    val <caret>foo: Int
+}

idea/testData/multiModuleQuickFix/memberValToExtensionByHeaderWithInapplicableImpl/js/js.kt

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

idea/testData/multiModuleQuickFix/memberValToExtensionByHeaderWithInapplicableImpl/jvm/jvm.kt

@@ -0,0 +1,3 @@
+impl class Foo {
+    impl val foo get() = 2
+}