Add a new launcher cli option to select the version to launch

[leMaik]

…and move the release channel into a distinct option.

This builds upon #1682 (which was never released, so the options change doesn't break anything) and allows stuff like java -jar ChunkyLauncher.jar --releaseChannel snapshot --chunkyVersion latest to launch the latest snapshot, even if the stable channel is the currently selected channel.

Also you can now download and launch PR builds with a single command ✨

java -jar ChunkyLauncher.jar \
  --updateSite https://chunky-pr.lemaik.de \
  --releaseChannel pr-1859 \
  --update \
  --chunkyVersion latest

[leMaik]

The second example above doesn't work because --update exits. I see how just updating might be useful.

Maybe we should switch to some library that supports subcommands, like picocli or JCommander?

[ThatRedox]

How would subcommands help?

[leMaik]

ChunkyLauncher.jar update to update and then exit
ChunkyLauncher.jar [launch] --update to update (optionally) and then start

[ThatRedox]

I think there should be a way to do that as is, but if you want to switch to a better CLI parsing library I'm not against it.

[leMaik]

@ThatRedox I found a workaround 🎉