Sort indices in Frame.bond.group

[chrisjonesBSU]

This is a quick change that sorts the particle indices before appending to Frame.bond.group. This should have no effect on bond types or typeids. The bond.group is just a list of length 2 with the particle indices in the bond.

The reason why I think we should do this is because the locality and neighbor list modules in freud require that the bond arrays are sorted. Also, I think its cleaner and easier to read if you're ever having to read these arrays manually for some reason.

I'm not sure why this was never a problem for me when using the hoomd writers in mBuild, maybe its some how related to how Parmed indexes particles in bonds.

[CalCraven]

This seems reasonable especially because getting things into a format for freud is good. Yeah it looks like things go to parmed systems. Could be a good test to make sure the mbuild snapshot writer handles this the same way as the gmso one.

[daico007]

Would it be easier/faster to sneak this into #765? Or would these clash/out-of-scope?

[daico007]

That #765 basically contains #762, which try to deal with all the sorting too

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (7537899) 92.82% compared to head (5192013) 92.81%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #769      +/-   ##
==========================================
- Coverage   92.82%   92.81%   -0.02%     
==========================================
  Files          66       66              
  Lines        6845     6845              
==========================================
- Hits         6354     6353       -1     
- Misses        491      492       +1     

Files Changed	Coverage Δ
gmso/external/convert_hoomd.py	92.02% <ø> (ø)

... and 1 file with indirect coverage changes

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[chrisjonesBSU]

We could definitely just include this in #765

[daico007]

I think the change is small enough, and that it has no impact on the other things (bond types and typeids), I think I gonna merge this and do a release of GMSO this morning. We could work on adding more tests later.