Localize shutdown message

Expected behavior

The localized message for multiplayer.disconnect.server_shutdown should be displayed

Observed/Actual behavior

When the server stops, everyone gets kicked with the default message Server closed, regardless of the client's locale.

Steps/models to reproduce

1. Start a server
2. Connect
3. Change your locale to something else then English
4. Stop the server

Plugin and Datapack List

pl
[10:28:14 INFO]: Server Plugins (13):
[10:28:14 INFO]: Paper Plugins:
[10:28:14 INFO]: - Commander, CreativeUtilities, goPaintAdvanced, Tweaks, Worlds
[10:28:14 INFO]: Bukkit Plugins:
[10:28:14 INFO]: - EasyArmorStands, FastAsyncVoxelSniper, FastAsyncWorldEdit, goBrush, LuckPerms, NoisyPatterns, Skulls, WorldEditSUI

datapack list
[10:28:17 INFO]: There are 3 data pack(s) enabled: [vanilla (built-in)], [file/bukkit (world)], [paper (built-in)]
[10:28:17 INFO]: There are no more data packs available

irrelevant

Paper version

This server is running Paper version 1.21-124-master@df3b654 (2024-08-02T00:02:38Z) (Implementing API version 1.21-R0.1-SNAPSHOT)
Affects every version though

Other

The shutdown message config entry inside the bukkit.yml should support MiniMessage and default to <lang:multiplayer.disconnect.server_shutdown> or fallback to the translated component if the entry is null (and be null by default)

Start by tracing how the shutdown message configured in bukkit.yml is selected and how the multiplayer.disconnect.server_shutdown translation is represented. Check the existing handling for MiniMessage and translated components, then verify that a null default uses the localized message and that an explicit configuration is honored.