Minor. Add tests to check returning inline class from default method

#KT-45539 Obsolete

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/boxReturnValueInDefaultMethod.kt

@@ -0,0 +1,15 @@
+// IGNORE_BACKEND: JVM
+
+interface X<T> {
+    operator fun plus(n: Int) : T
+    fun next(): T = this + 1
+}
+
+inline class A(val value: Int) : X<A> {
+    override operator fun plus(n: Int) = A(value + n)
+}
+
+fun box(): String {
+    val res = A(1).next()
+    return if (res.value == 2) "OK" else "FAIL $res"
+}