Update port.access_labels

[daico007]

PR Summary:

Address #1031, add extra check for port access labels from its root compound. Change port.access_labels to be set to avoid duplicated labels.

PR Checklist

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• Includes appropriate unit test(s)
• Appropriate docstring(s) are added/updated
• Code is (approximately) PEP8 compliant
• Issue(s) raised/addressed?

[CalCraven]

Probably just good to add a test similar to what you have in issue #1031 that validates all the port labels are accessible.

[codecov]

Codecov Report

Merging #1032 (482fef1) into main (bcbf980) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1032   +/-   ##
=======================================
  Coverage   90.36%   90.37%           
=======================================
  Files          64       64           
  Lines        9011     9014    +3     
=======================================
+ Hits         8143     8146    +3     
  Misses        868      868           

Impacted Files	Coverage Δ
mbuild/port.py	98.86% <100.00%> (+0.04%)	⬆️

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[CalCraven]

Nice fix!