Stop FileWatcher default instance on dedicated server exit

[sciwhiz12]

This PR fixes #1626 by stopping the default FileWatcher instance when the dedicated server instance exits (from DedicatedServer#onServerExit()).

This prevents the FileWatcher instance from blocking the JVM from exiting normally, as the instance keeps alive a non-daemon thread (and the JVM waits on all non-daemon threads to exit).

This is meant to be a temporary bugfix, until a bugfix is landed in NightConfig that marks the pool thread it creates as a daemon thread. (Follow the linked issue for more details.)

Tested by following the listed reproduction steps in the issue (which is important, since the FileWatcher has to be triggered once for the erring pool thread to be made), and observing that the JVM does exit soon after the server is stopped through /stop.

---

Out of the 'normal' runs, the dedicated server is affected. The client and the game test server exit the JVM using System.exit, as seen in Minecraft#destroy and GameTestServer#onServerExit respectively. The datagenerator, both client and server, does not load the configs, as seen in CommonModLoader#begin.

The JUnit server might be affected, but I am unsure if it is truly affected, since it may be that JUnit itself does a System.exit at the end of testing to handle the exit codes itself. I'm leaning towards the possibility that it is unaffected due to the special considerations of JUnit.

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: c472ab2bc31359280b13fa2e30cfdecf93cdd685.

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged:testframework:21.4.15-beta-pr-1757-1.21.4-GH-1626-filewatcher-dediserver-shutdown
• 📦 net.neoforged:neoforge:21.4.15-beta-pr-1757-1.21.4-GH-1626-filewatcher-dediserver-shutdown

Repository Declaration

In order to use the artifacts published by the PR, add the following repository to your buildscript:

repositories {
    maven {
        name 'Maven for PR #1757' // https://github.com/neoforged/NeoForge/pull/1757
        url 'https://prmaven.neoforged.net/NeoForge/pr1757'
        content {
            includeModule('net.neoforged', 'testframework')
            includeModule('net.neoforged', 'neoforge')
        }
    }
}

MDK installation

In order to setup a MDK using the latest PR version, run the following commands in a terminal.
The script works on both *nix and Windows as long as you have the JDK bin folder on the path.
The script will clone the MDK in a folder named NeoForge-pr1757.
On Powershell you will need to remove the -L flag from the curl invocation.

mkdir NeoForge-pr1757
cd NeoForge-pr1757
curl -L https://prmaven.neoforged.net/NeoForge/pr1757/net/neoforged/neoforge/21.4.15-beta-pr-1757-1.21.4-GH-1626-filewatcher-dediserver-shutdown/mdk-pr1757.zip -o mdk.zip
jar xf mdk.zip
rm mdk.zip || del mdk.zip

To test a production environment, you can download the installer from here.

[embeddedt]

This is a fairly major bug, we should ideally backport the fix to 1.21.1 as well.

[TelepathicGrunt]

Will merge if no objections by tomorrow (like 8 hours from now lol)

[neoforged-releases]

🚀 This PR has been released as NeoForge version 21.4.17-beta.