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/kt45853.kt

@@ -0,0 +1,18 @@
+// FILE: kt45853.kt
+open class MyProblem() : ThrowableProblem() {
+    override fun getCause(): Exceptional? = super.cause
+}
+
+// FILE: Exceptional.java
+public interface Exceptional {
+    Exceptional getCause();
+}
+
+// FILE: ThrowableProblem.java
+public abstract class ThrowableProblem extends RuntimeException implements Exceptional  {
+    @Override
+    public ThrowableProblem getCause() {
+        // cast is safe, since the only way to set this is our constructor
+        return (ThrowableProblem) super.getCause();
+    }
+}