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/jerry/array-prototype-unshift.js

@@ -123,3 +123,7 @@ try {
 } catch (e) {
   assert(e instanceof TypeError);
 }
+
+var arrayLike = {get 5() { throw "shouldn't throw"; }};
+arrayLike.length = 10;
+Array.prototype.unshift.call(arrayLike);