Fix plugin messages for Floodgate players

[Smart123s]

Summary of your change

Previously registration checks for Floodgate players were made via, authPlugin.isRegistered(username). However, if no auth plugin is installed, that it would have obviously failed. With this PR, if there's no such plugin, it'll try to get the registration status from the SQL Database.

Related issue

Fixes #594

I got a lot of java.lang.IllegalStateException: Cannot reply to EncryptionRequestPacket without profile and access token. errors while trying to join via Bungeecord. It happens randomly (around 50% of the time), if the player is not yet in the Floodgate.getPlayers() list when doing the name conflict checking:
https://github.com/games647/FastLogin/blob/01c9b55d80c93e0df4ad9050519995f4d56db759/core/src/main/java/com/github/games647/fastlogin/core/shared/JoinManagement.java#L61

This error is unrelated to the files modified in this PR, so I thought that I'd open a second PR with the fix #603 because I couldn't figure it out.

[Smart123s]

I've tested the plugin again (now on a working server), and I got an error on my Paper instance:

[19:34:42 INFO]: UUID of player .Smart123s is 00000000-0000-0000-00...
[19:34:42 INFO]: [floodgate] Floodgate player logged in as .Smart123s joined (UUID: 00000000-0000-0000-00...)
[19:34:42 INFO]: .Smart123s joined the game
[19:34:42 INFO]: .Smart123s[/192.168.1.212:41703] logged in with entity id 294 at ([world]133.5, 65.0, 6.5)
[19:34:42 INFO]: [FastLogin] Player info REGISTER command for .Smart123s from proxy
[19:34:42 INFO]: [FastLogin] Delaying force login until join event fired?: false
[19:34:42 WARN]: [AuthMe] Could not save LimboPlayer for '.Smart123s' [InaccessibleObjectException]: Unable to make private java.util.Collections$EmptyList() accessible: module java.base does not "opens java.util" to unnamed module @157853da
[19:34:43 INFO]: [FastLogin] Player .Smart123s is connecting through Geyser Floodgate.
[19:34:43 WARN]: [FastLogin] Plugin FastLogin v1.11-SNAPSHOT-172efaf generated an exception while executing task 777
java.lang.NullPointerException: Cannot invoke "com.github.games647.fastlogin.core.storage.SQLStorage.loadProfile(String)" because the return value of "com.github.games647.fastlogin.core.shared.FastLoginCore.getStorage()" is null
        at com.github.games647.fastlogin.core.shared.FloodgateManagement.run(FloodgateManagement.java:76) ~[FastLoginBukkit.jar:?]
        at org.bukkit.craftbukkit.v1_17_R1.scheduler.CraftTask.run(CraftTask.java:101) ~[patched_1.17.1.jar:git-Paper-214]
        at org.bukkit.craftbukkit.v1_17_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:54) [patched_1.17.1.jar:git-Paper-214]
        at com.destroystokyo.paper.ServerSchedulerReportingWrapper.run(ServerSchedulerReportingWrapper.java:22) [patched_1.17.1.jar:git-Paper-214]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) [?:?]
        at java.lang.Thread.run(Thread.java:831) [?:?]

Is it normal that FastLoginCore.getStorage() is null on Paper, if it's running in Bungee mode? I'll add an exclusion if it is.

[TuxCoding]

Yes, spigot server doesn't need storage access then.