Update Java version

Because more recent versions of Minecraft are using later versions of Minecraft, as well as SpringBoot Artemis apparently no longer putting out updates for Java 8, an update to the used JDK is in order.

Java Development Kit (JDK) 18 has moved into a final release candidate stage, as of February 24. The new version of standard Java, due in a final release March 22, 2022, will have nine new features. Upgrades to standard Java are released every six months; the previous version, JDK 17, arrived in September.

Though which version will ultimately end up being used depends on when Milestone 3.x as been finished. The Java Update should consider the following list and their respective LTS releases

https://www.oracle.com/java/technologies/java-se-support-roadmap.html

So, as of me writing this, the version to update to should be Java 17 (LTS).

Should Milestone 3.x be finished close to September 2023, then 21 (LTS) should be considered.