Label OmniUnits as Omni in the MekHQ UI

[WeaverThree]

Omni units have different rules in regards to refits and such that matter in MekHQ more than in MegaMek, so I thought it would be nice to distinguish them a little more clearly.

Omni units sort after non-omni units of the same type.

Unit list filters don't change, e.g. OmniMeks and Meks are both listed under the Mek filter.

Also kills a couple deprecaiton warnings along the way.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 10.52%. Comparing base (3352c18) to head (5b29f78).
Report is 23 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5121      +/-   ##
============================================
- Coverage     10.54%   10.52%   -0.02%     
+ Complexity     6040     6032       -8     
============================================
  Files           956      956              
  Lines        134181   134241      +60     
  Branches      19481    19497      +16     
============================================
- Hits          14144    14129      -15     
- Misses       118693   118760      +67     
- Partials       1344     1352       +8     

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