Execute chunk loading operations outside the main thread

[szumielxd]

Overview

Description

Now, main command will wait with further execution until plot center location is asynchronously obtained. This will free the main thread while reaching plot in unloaded chunk

Submitter Checklist

• Make sure you are opening from a topic branch (/feature/fix/docs/ branch (right side)) and not your main branch.
• Ensure that the pull request title represents the desired changelog entry.
• New public fields and methods are annotated with @since TODO.
• I read and followed the contribution guidelines.

[PierreSchwang]

Can't see any obvious errors, and seems to be working ingame. My only nitpicks currently are

• Use a Logger instead of Throwable#printStackTrace
• I think we are using javax Annotations, instead of Jetbrains Annotations (not 100% sure on that though - another review is required either way)

[dordsor21]

I would address the above things Pierre raised before merge - we should avoid merging code "smells"

[szumielxd]

To be honest, It's hard to get any information about correct code-styling. I can easly find a file with both - NotNull and NonNull annotations. But I'm more than happy to modify my PR to use javax if that's the correct one.