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

js/js.translator/testData/box/char/charBinaryOperations.kt

@@ -0,0 +1,11 @@
+package foo
+
+fun box(): String {
+
+    assertEquals('K', 'A' + 10)
+    assertEquals('7', 'A' - 10)
+
+    assertEquals(3, 'd' - 'a')
+
+    return "OK"
+}