Miscellaneous trait look-up reductions

[reaperrr]

Some more trait look-up reductions in places that might not get called that often, but potentially several times at once.

I was too lazy to measure the performance impact (unlikely to be noteworthy, anyway), but those felt simple enough to pass as "can't hurt and might add up, without regressing or over-complicating code".

[anvilvapre]

Mods won't be able to add multiple Mobile traits to an actor? In the past it would cause an exception during trait lookup. Now it would cause OccupiesSpace to be used?

[reaperrr]

Updated
Removed first commit less because of the comment, but more because attempted profiling showed MoveAdjacentTo to be far less common than I thought.

Didn't bother profiling the Mobile.Pathfinder changes since that's more polish than anything.

Perf improvements from the 2 CanAttack changes, from left to right (bleed, armament changes only, both), in stopwatch ticks:

[pchote]

Looks reasonable to me, just had a couple of small style nits.

[reaperrr]

Updated.

[abcdefg30]

Code changes lgtm but untested

[pchote]

https://github.com/OpenRA/OpenRA/wiki/Changelog-(bleed)/_compare/2259475ff1e3ce0f818821bb82eb208b0fea8960