Add another test for KT-49715 and fix JS IR behavior

#KT-49715
 #KT-51798 Fixed

compiler/testData/codegen/box/dataClasses/kt49715_behaviorChange.kt

@@ -0,0 +1,17 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// FIR status: [IR VALIDATION] Duplicate IR node: FUN GENERATED_DATA_CLASS_MEMBER name:equals
+
+interface A {
+    fun Any.equals(other: Any?): Boolean = false
+    fun Any.hashCode(): Int = 0
+    fun Any.toString(): String = ""
+}
+
+data class B(val x: Int) : A
+
+fun box(): String {
+    if (B(42) != B(42)) return "Fail equals"
+    if (B(42).hashCode() != B(42).hashCode()) return "Fail hashCode"
+    if (B(42).toString() != B(42).toString()) return "Fail toString"
+    return "OK"
+}