Patches for element reading in lattice builder

[CalCraven]

PR Summary:

This is a small patch to check for element information from the lattice reader. This is relevant if the user doesn't pass a compund dict of the form {name(STR): compound(mb.Compound)} to map the lattice points to a specific compound. In this case, the only information the populate function has is the key for each lattice point, which is a string. We can then use the ele package to check if that is supposed to be an element. Like always, if this is a coarse grained bead without element information, use an _NAME syntax to denote that, and no element information will be found.

Usage:

lattice = mb.Lattice(
             lattice_spacing=[0.5, 0.5, 1],
             angles=[90, 90, 120],
             lattice_points={"O": [[0, 0, 0]]},
 )
 cpd_lat = lattice.populate(x=1, y=1, z=1)
 for part in cpd_lat:
     assert part.element.name == "oxygen" # the oxygen is identified from the lattice_points dict.

PR Checklist

---

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

Closes #1065.

[daico007]

LGTM!

[codecov]

Codecov Report

Base: 90.69% // Head: 90.71% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (2b2b86a) compared to base (ee91caa).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1066      +/-   ##
==========================================
+ Coverage   90.69%   90.71%   +0.02%     
==========================================
  Files          57       57              
  Lines        5500     5513      +13     
==========================================
+ Hits         4988     5001      +13     
  Misses        512      512              

Impacted Files	Coverage Δ
mbuild/lattice.py	96.81% <100.00%> (+0.19%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[daico007]

Failing tests come from the new energy minimization with Windows (py39). I might have overlooked this when merging the other PR, but I think we should just skip those test on windows run.

[bc118]

LGTM