Add-ons Redis Cache By Xon 2.18.3

• Fix case where cached forum thread counts may be inaccurate due to insufficiently specific cache key

• Update library used to talk to redis to version which is confirmed php 8.1 compatible
• Improve compatibility with 3rd party add-ons with caching applied to user's online list

• Fix email rendering
• Prefix known global functions to avoid a current namespace lookup for the function.
• Work-around for non-desirable caching behaviour when CloudFlare (or similar) is forced to cache css.php output
  • If css.php would return empty output instead return a 404 and cache in redis for at most a second
  • Prevent polluting of caches if the time-stamp is in the future
• Improve XF Cloud support
  • config.php are not required if the stock Redis connector is used.
  • Currently XF Cloud does not use Redis for the main cache which prevents various redis-only add-ons from functioning as expected