Checkstyle: Fix naming violations in attachments (T-U)

[ssoloff]

Overview

Fixes violations of the Checkstyle MemberName rule in the TerritoryAttachment, TerritoryEffectAttachment, UnitSupportAttachment, and UserActionAttachment classes.

Functional Changes

None.

Manual Testing Performed

None.

[codecov-io]

Codecov Report

Merging #4222 into master will decrease coverage by 0.02%.
The diff coverage is 50%.

@@             Coverage Diff              @@
##             master    #4222      +/-   ##
============================================
- Coverage     22.61%   22.58%   -0.03%     
+ Complexity     6114     6107       -7     
============================================
  Files           870      870              
  Lines         71370    71370              
  Branches      11395    11395              
============================================
- Hits          16137    16118      -19     
- Misses        53168    53188      +20     
+ Partials       2065     2064       -1

Impacted Files	Coverage Δ	Complexity Δ
...tegy/triplea/attachments/UserActionAttachment.java	3.61% <20%> (ø)	1 <1> (ø)	⬇️
...ategy/triplea/attachments/TerritoryAttachment.java	40.37% <41.66%> (ø)	59 <24> (ø)	⬇️
...triplea/attachments/TerritoryEffectAttachment.java	58.97% <47.61%> (ø)	16 <3> (ø)	⬇️
...egy/triplea/attachments/UnitSupportAttachment.java	70.81% <68.18%> (ø)	51 <23> (ø)	⬇️
...engine/framework/map/download/FileSizeWatcher.java	0% <0%> (-71.43%)	0% <0%> (-4%)
...gy/engine/framework/map/download/DownloadFile.java	36.95% <0%> (-13.05%)	9% <0%> (-1%)
.../games/strategy/engine/ClientFileSystemHelper.java	55% <0%> (-2.5%)	10% <0%> (-1%)
.../src/main/java/games/strategy/net/nio/Decoder.java	72.82% <0%> (-2.18%)	24% <0%> (-1%)

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[RoiEXLab]

Just mentioning it here because I don't think it has been noted elsewhere since we broke compatibility:
We should change the type of the collection implementations to the interface type to be able to change the type in other places as well.
Also we should have a look at all places in the code where a TODO comment contains the world incompatible.

[ssoloff]

@RoiEXLab I added the items you noted to the task list of #2827.