Convert normal arrays to custom Vectors as they show order of magnitude improvement

[LouisJenkinsCS]

The Vector implementation in Vector.chpl outperforms Chapel Array push_back by 10x and so we should see significant improvement once this conversion has completed.

Push-Back: 8.92253 seconds
Append: 0.91275 seconds

[LouisJenkinsCS]

Also makes it possible to do the 1.5D arrays as the Vector can be parameterized on the domain which may or may not be distributed.

[LouisJenkinsCS]

A better way to do this, for the meantime at least, is to just implement vector logic for neighborList by having a separate counter (perhaps atomic so that it may be accessible without acquiring lock).

[github-actions]

This issue is stale and should either be closed or eventually resolved.