Extract Class: Implement 'Extract Interface' refactoring

#KT-11017 Fixed

idea/testData/refactoring/extractInterface/addInterface.kt

@@ -0,0 +1,13 @@
+// NAME: X
+// INFO: {checked: "true"}
+interface T {}
+
+open class A
+
+// SIBLING:
+class <caret>B : A(), T {
+    // INFO: {checked: "true"}
+    fun foo() {
+
+    }
+}