AI - Add support for placing triggered sea units

[ron-murhammer]

Addresses feedback here: https://forums.triplea-game.org/topic/105/ai-development-discussion-and-feedback/97

The AI will now try to place any remaining sea units (previously only tried to place land/air).

[codecov-io]

Codecov Report

Merging #3542 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master    #3542      +/-   ##
============================================
- Coverage     21.98%   21.97%   -0.01%     
+ Complexity     5922     5919       -3     
============================================
  Files           838      838              
  Lines         71991    72000       +9     
  Branches      11551    11553       +2     
============================================
- Hits          15828    15824       -4     
- Misses        54075    54086      +11     
- Partials       2088     2090       +2

Impacted Files	Coverage Δ	Complexity Δ
...a/games/strategy/triplea/ai/pro/ProPurchaseAi.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...rategy/triplea/attachments/UnitTypeComparator.java	46.15% <0%> (-7.7%)	12% <0%> (-1%)
.../strategy/triplea/odds/calculator/DummyPlayer.java	35.22% <0%> (-1.14%)	9% <0%> (-1%)
.../src/main/java/games/strategy/net/nio/Decoder.java	72.82% <0%> (-1.09%)	24% <0%> (-1%)

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[ron-murhammer]

Merging as minor AI change so it can be tested.