Add config option for player name regex

[TPGamesNL]

Description

Adds a config option for the player name regex pattern.

Also includes changes from #4367, thanks @AyhamAl-Ali for that!

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Target Minecraft Versions: any
Requirements: none
Related Issues: #4374, #4367

[SaFiKiK]

Could you please change the min length from 1 to 3, since min. allowed nickname length is 3? It will make less unneeded Bukkit API calls if players make mistakes in commands

[TheLimeGlass]

There are still player names with 2 characters. Although extremely rare they'll join your server, there are a few accounts.

I believe Mojang confiscated the accounts that were inactive or compromised, but still allowed 2 letter account names that were active.

There is a Youtube documentary on the user that still actively plays on Xa or Xe.

[TheBentoBox]

There are people with 1 letter names too. The person named "G" joined my server a handful of years ago. They were still active as of 2019 too, at which point they swapped to a lowercase "g". It should be left as 1 character min.

[TheLimeGlass]

If we want to be reducing Mojang API lookups, we can loop Bukkit.getOfflinePlayers() first, which doesn't do API calls then use the Bukkit method. We can also cache OfflinePlayers that get returned, although I think the Bukkit server does this. I couldn't find any information if the server caches the results itself.

[TPGamesNL]

In that case I'll change it back to a minimum of 1 character (I'm just gonna assume Mojang did not allow a 0 character name).