Improved logic to determine which plots to update on chunk load/unload

[InstantlyMoist]

Overview

Description

I noticed high usage from this plugin when it comes to joining an empty plot world, after debugging I found out that it called createOrUpdateHologram multiple times for the same plot, sometimes up to 11 times.

To mitigate this issue, I check the 4 corners of the loaded chunk and check if the sign position falls within this chunk. Whilst also keeping track we haven't processed this chunk yet. This reduced my updates from 6-11 per plot to 1.

Open to feedback, this solution made sense to me as the sign location is 'one case'.

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.