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

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

@@ -0,0 +1,18 @@
+package foo
+
+class A
+
+fun box(): String {
+
+    assertEquals(false, ('A' as Any) is Int)
+    assertEquals(false, ('A' as Any) is Short)
+    assertEquals(false, ('A' as Any) is Byte)
+    assertEquals(false, ('A' as Any) is Float)
+    assertEquals(false, ('A' as Any) is Double)
+    assertEquals(false, ('A' as Any) is Number)
+
+    assertEquals(true, 'A' is Char)
+    assertEquals(true, ('A' as Any) is Char)
+
+    return "OK"
+}