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.c

@@ -866,8 +866,6 @@ main (void)
     jerry_cleanup ();
   }
 
-  /* Test parsing/executing scripts with lexically scoped global variables multiple times. */
-  if (jerry_feature_enabled (JERRY_FEATURE_SYMBOL))
   {
     jerry_init (JERRY_INIT_EMPTY);
     const jerry_char_t scoped_src_p[] = "let a; this.b = 5";