Extract Class: Implement 'Extract Interface' refactoring

#KT-11017 Fixed

idea/testData/refactoring/extractInterface/addInterfaceWithAbstract.kt.after

@@ -0,0 +1,18 @@
+// NAME: X
+// INFO: {checked: "true"}
+interface T {}
+
+open class A
+
+interface X : T {
+    // INFO: {checked: "true", toAbstract: "true"}
+    fun foo()
+}
+
+// SIBLING:
+class B : A(), X {
+    // INFO: {checked: "true", toAbstract: "true"}
+    override fun foo() {
+
+    }
+}