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-api-object-property-names.c

@@ -80,11 +80,6 @@ define_property (const jerry_value_t object,
 int
 main (void)
 {
-  if (!jerry_feature_enabled (JERRY_FEATURE_SYMBOL))
-  {
-    return 0;
-  }
-
   TEST_INIT ();
   jerry_init (JERRY_INIT_EMPTY);