JS: create new common directory for all generated tests, migrate several tests there

js/js.translator/testData/box/dataClass/override.kt

@@ -0,0 +1,25 @@
+package foo
+
+var t: Any? = null
+
+data class Dat(val start: String, val middle: String, val end: String) {
+    override fun toString() = "another string"
+    override fun hashCode() = 371
+    override fun equals(other: Any?): Boolean {
+        t = other
+        return true
+    }
+}
+
+fun box(): String {
+    val d = Dat("max", "-", "min")
+    val other = Dat("other", "-", "instance")
+
+    assertEquals(371, d.hashCode())
+    assertEquals(true, d == other)
+    assertEquals(other, t)
+    assertEquals("another string", d.toString())
+
+    return "OK"
+}
+