[FIR] Add regression test for overriding Java with DNN without annotations

#KT-58933 Related

compiler/testData/diagnostics/tests/override/dnnOverridesFlexible.fir.kt

@@ -0,0 +1,14 @@
+// ISSUE: KT-58933
+// FILE: J.java
+public interface J<T> {
+    void simple(T t);
+    void box(Box<T> box);
+}
+
+// FILE: test.kt
+class Box<T>
+
+class K<T> : J<T> {
+    override fun simple(t: T & Any) {}
+    override fun box(box: Box<T & Any>) {}
+}

compiler/testData/diagnostics/tests/override/dnnOverridesFlexible.kt

@@ -0,0 +1,14 @@
+// ISSUE: KT-58933
+// FILE: J.java
+public interface J<T> {
+    void simple(T t);
+    void box(Box<T> box);
+}
+
+// FILE: test.kt
+class Box<T>
+
+<!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>class K<!><T> : J<T> {
+    <!NOTHING_TO_OVERRIDE!>override<!> fun simple(t: T & Any) {}
+    <!NOTHING_TO_OVERRIDE!>override<!> fun box(box: Box<T & Any>) {}
+}