#5956: Ice-related skidding PSR checks (underwater movement etc)

[SJuliez]

Adds an elevation check so that units only skid on ice when at elevation 0 = on the ice, not under or above it.

Fixes #5956
Climb mode affects how a mek moves when in depth 2 water. In "thru" climb it'll stay at the bottom, otherwise (default) it'll try to climb and may fall back in

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.17%. Comparing base (336ba8f) to head (eccae84).
Report is 58 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6168      +/-   ##
============================================
- Coverage     29.19%   29.17%   -0.02%     
+ Complexity    13974    13972       -2     
============================================
  Files          2623     2628       +5     
  Lines        266435   266546     +111     
  Branches      47594    47572      -22     
============================================
- Hits          77775    77773       -2     
- Misses       184755   184889     +134     
+ Partials       3905     3884      -21     

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[pavelbraginskiy]

Does this work if the hex is on a hill, so the surface of the ice isn't at level 0?

[SJuliez]

Elevation is relative to hex level, so ice can only be at elevation 0, meaning it should work which is not to say that it might not actually fail.

[pavelbraginskiy]

Hmm, there might still be an edge-case for bridges.

I'm not very familiar with how bridges or ice work in megamek, so maybe this isn't a possible scenario after all, but I believe under the rules you could conceivably have black ice on a bridge surface, with ice covering the water underneath the bridge, in which case you would have ice at two different elevations in one hex.

[SJuliez]

ok, updated the code to handle black ice on bridges. Should be good now