Cleanup related to new naming scheme and refactoring, fixes refits to blank model names.

[Setsul]

Removed old kludges obsoleted by getFullChassis()
Refactoring of retrieveOriginalUnit() to enable
refactoring of populateRefits() that properly throws exceptions.

This fixes the bug that ever since (Standard) was purged from model names, those models with now blank names stopped showing up as targets for refits in the GUI.
And if something similar happens again we will get an EntityLoadingException now.

Screenshots from 49.7 (last milestone before the bug) vs 50.0 vs this commit for illustration purposes.

[IllianiCBT]

Welcome to the project :)

[IllianiCBT]

@WeaverThree given your recent work on refits, can you chuck your eyes over this PR and confirm if it looks good. Code-wise, I'm not seeing anything obviously wrong, but I've got zero experience with this corner of the code.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 10.46%. Comparing base (4e72790) to head (9173982).
Report is 81 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5031      +/-   ##
============================================
- Coverage     10.47%   10.46%   -0.01%     
+ Complexity     6029     6027       -2     
============================================
  Files           950      950              
  Lines        133397   133462      +65     
  Branches      19384    19390       +6     
============================================
- Hits          13974    13970       -4     
- Misses       118076   118146      +70     
+ Partials       1347     1346       -1     

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[Setsul]

Weaver did almost instantly point me at the line that was causing the problem, so credit where credit is due.

They did look over it already and chose this version over a literal 1 line fix that left the accumulated cruft in place, for obvious reasons, so I expect we'll get their official blessing shortly.

[WeaverThree]

Looks good to me. I checked out retrieveOriginalUnit() and found that it's a single-client function used in Refit.saveCustomization(), which i checked and it still works fine :>. I also tested that it fixed the issue, and it did, it let me refit a Warhammer IIC 2 to a plain Warhammer IIC no problem.

[IllianiCBT]

Perfect, thanks for taking a look :)