Remove ES_NEXT macro (#4915)

- remove all '#JERRY_ESNEXT' macro
- remove 5.1 build profile, update test runner accordingly (Note: all builtins are turn on by default)
- move tests from tests/jerry/esnext into tests/jerry, concatenate files with same names
- add skiplist to some snapshot tests that were supported only in 5.1
- fix doxygen issues that were hidden before (bc. of es.next macro)

Co-authored-by: Martin Negyokru negyokru@inf.u-szeged.hu
JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/unit-core/test-promise-callback.c

@@ -123,12 +123,6 @@ main (void)
 {
   TEST_INIT ();
 
-  if (!jerry_feature_enabled (JERRY_FEATURE_PROMISE))
-  {
-    jerry_log (JERRY_LOG_LEVEL_ERROR, "Promise is disabled!\n");
-    return 0;
-  }
-
   /* The test system enables this feature when Promises are enabled. */
   TEST_ASSERT (jerry_feature_enabled (JERRY_FEATURE_PROMISE_CALLBACK));