MDEV-35614: json_unescape for comparison uses utf8mb4_bin

Author: grooverdan

sql/item_jsonfunc.cc

@@ -4120,7 +4120,7 @@ int Arg_comparator::compare_json_str_basic(Item *j, Item *s)
  if (value2.realloc_with_extra_if_needed(je.value_len) ||
  (c_len= json_unescape(js->charset(), je.value,
  je.value + je.value_len,
- &my_charset_utf8mb3_general_ci,
+ &my_charset_utf8mb4_bin,
  (uchar *) value2.ptr(),
  (uchar *) (value2.ptr() + je.value_len))) < 0)
  {
@@ -4175,7 +4175,7 @@ int Arg_comparator::compare_e_json_str_basic(Item *j, Item *s)
  if (value1.realloc_with_extra_if_needed(value_len) ||
  (c_len= json_unescape(value1.charset(), (uchar *) value,
  (uchar *) value+value_len,
- &my_charset_utf8mb3_general_ci,
+ &my_charset_utf8mb4_bin,
  (uchar *) value1.ptr(),
  (uchar *) (value1.ptr() + value_len))) < 0)
  {