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/ecma/operations/ecma-big-uint.c

@@ -1473,8 +1473,6 @@ ecma_big_uint_shift_right (ecma_extended_primitive_t *left_value_p, /**< left Bi
   return ecma_big_uint_increase_result (result_value_p);
 } /* ecma_big_uint_shift_right */
 
-#if JERRY_ESNEXT
-
 /**
  * Compute the left value raised to the power of right value
  *
@@ -1545,8 +1543,6 @@ ecma_big_uint_pow (ecma_extended_primitive_t *left_value_p, /**< left BigUInt va
   return result_p;
 } /* ecma_big_uint_pow */
 
-#endif /* JERRY_ESNEXT */
-
 /**
  * Perform bitwise operations on two BigUInt numbers
  *