Simple ability self profiler

[robojumper]

Helps towards #1044.

@Xymanek suggested:

add an array to CHHelpers for ability templates to force usage of script GAT (XCGS_A_CH), so that we can see what exact part of logic is spending so much time. The DoesBlockUnitPathing calls makes me suspect that we are actually spending the time in X2AbilityTarget_MovingMelee/pathfinding

[robojumper]

Flash of inspiration: We don't strictly need XCGS_A_CH for profiling -- we can just add a denativized GatherAbilityTargets function with a different name that's called for specific abilities instead. We can even add code to record the number of initial targets, filtered targets etc.

[robojumper]

Note to self: This should be final.