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

jerry-core/parser/js/js-parser-util.c

@@ -752,8 +752,6 @@ parser_set_continues_to_current_position (parser_context_t *context_p, /**< cont
   }
 } /* parser_set_continues_to_current_position */
 
-#if JERRY_ESNEXT
-
 /**
  * Return the size of internal record corresponding to a class field
  *
@@ -867,8 +865,6 @@ parser_reverse_class_fields (parser_context_t *context_p, /**< context */
   parser_free (data_p, fields_size);
 } /* parser_reverse_class_fields */
 
-#endif /* JERRY_ESNEXT */
-
 /**
  * @}
  * @}