CommandMapUtil's reflection to the SimplePluginManager commandMap and SimpleCommandMap knownCommands fields should ideally be replaced by Paper-specific APIs, namely Server#getCommandMap and CommandMap#getKnownCommands, where these methods exist.

Doing so will improve the stability of spark in case of implementation changes in Bukkit-based server software.

I'll accept a PR for this as long as the code stays neat/tidy :)