Add new tests

compiler/testData/codegen/box/jvm8/defaults/allCompatibility/interfaceExtension.kt

@@ -0,0 +1,13 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// !JVM_DEFAULT_MODE: all-compatibility
+// TARGET_BACKEND: JVM
+// JVM_TARGET: 1.8
+// WITH_RUNTIME
+interface A {
+    fun String.foo(k: String) = "O" + k
+}
+
+fun box(): String =
+    object : A {
+        fun box() = "FAIL".foo("K")
+    }.box()