Extract Function: Allow to choose between function and property extraction

idea/testData/refactoring/extractFunction/asProperty/extractToClass.kt.after

@@ -0,0 +1,15 @@
+// EXTRACT_AS_PROPERTY
+
+class A(val n: Int = 1) {
+    val m: Int = 2
+    // SIBLING:
+    fun foo(): Int {
+        return i
+    }
+
+    private val i: Int
+        get() {
+            return m + n + 1
+        }
+}
+