add official 1.20.6 support

[NonSwag]

Description

This PR adds official support for 1.20.6

• cloud command framework was updated to utilize the latest addition of paper brigadier
• use gooolers shadowJar fork for java 21 support
• updated hangar publish and removed dead code from publication task
• updated workflows to use java 21
• removed dead versions from "supported" list

Checklist

• I included all information required in the sections above
• I tested my changes and approved their functionality
• I ensured my changes do not break other parts of the code

[TheMeinerLP]

It would be nice to have changes that are not specific to PR. “Dependency updates, Gradle Update” should be made separately so that not everything has to be tested at once. If necessary, a component can already break something else

[NonSwag]

I could split it up into plugins, java and gradle update
and cloud update

[TheMeinerLP]

That would be perfect, I would be very happy with that

[NonSwag]

split up into #11, #12 and #13