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

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

@@ -0,0 +1,15 @@
+package foo
+
+fun box(): String {
+
+    assertEquals(true, 'B' in 'A'..'D')
+    assertEquals(true, 'E' !in 'A'..'D')
+
+    var s = ""
+    for(char in 'A'..'D') {
+        s += char
+    }
+    assertEquals("ABCD", s)
+
+    return "OK"
+}