Mindustry v8 compat

[phinner]

• Bumped Mindustry version to v8.
• Removed v7 build task (if someone needs to run an older claj server, he should use an older claj release).
• Tried to fix publishing because only the root project "claj" is published and not the components, did not really succeeded.
• Fixed javadoc because it was only applied to the root project and not the subprojects.
• Updated CI to use the latest actions versions.
• Fixed runMindustryDesktop task and added an additional one for local testing.

[ZetaMap]

thanks, i taken the build script and workflow parts, and credit you in the commit.