JS: move expressions test to box tests

js/js.translator/testData/box/expression/cast/implicitCastToLong.kt

@@ -0,0 +1,15 @@
+package foo
+
+fun box(): String {
+    var a: Long = 23
+    var b: Long = 200 + 30
+    var c: Long = id((2000).plus(300))
+
+    assertEquals(24L, a + 1)
+    assertEquals(231L, b + 1)
+    assertEquals(2301L, c + 1)
+
+    return "OK"
+}
+
+fun id(x: Long) = x