JVM_IR KT-45853 include return type into Java method IdSignature

This is a hack required to accept [potentially] incorrect input
provided by the front-end; see KT-46042.

compiler/testData/codegen/bytecodeListing/kt45853a.kt

@@ -0,0 +1,21 @@
+// FILE: kt45853a.kt
+abstract class A {
+    open val a: A? get() = null
+}
+
+class B() : AX() {
+    override fun getA(): X? = super.a
+}
+
+// FILE: X.java
+public interface X {
+    X getA();
+}
+
+// FILE: AX.java
+public abstract class AX extends A implements X {
+    @Override
+    public AX getA() {
+        return (AX) super.getA();
+    }
+}