convert to instance/move instance: support default methods in interfaces for java 8 (IDEA-154833)

java/java-tests/testData/refactoring/convertToInstance8Method/Interface2.java.after

@@ -0,0 +1,16 @@
+interface I {
+    default void m() {
+    }
+}
+
+class C implements I {
+}
+
+interface J extends I {
+}
+
+class D extends C implements J {
+}
+
+class X {
+}