[IR][tests] Add tests for removal-of-overridden open callable case

compiler/testData/klibABI/removeOpenFunction/lib2/l2.kt

@@ -0,0 +1,7 @@
+class C2 : C() {
+    override fun foo(): String = "O" // does not call super
+}
+
+class I2 : I {
+    override fun foo(): String = "K" // does not call super
+}

compiler/testData/klibABI/removeOpenFunction/lib2/module.info

@@ -0,0 +1,2 @@
+STEP 0:
+    dependencies: stdlib, lib1