Shared cooldown support

[xpdota]

Adds sharesCooldownWith field to Cooldown. If you want A, B, C, and D to have shared cooldowns, then B/C/D should have sharesCooldownWith: A.

The source and target cooldowns can have different CDs. If one has a 60s CD, and one has a 120s CD, then the cooldown time will be derived from whichever you actually use. That is, using the first skill would block both skills for 60s, and using the second would block both skills for 120s.

Behavior is undefined for abilities with more than one charge.

[xiashtra]

Adds sharesCooldownWith field to Cooldown. If you want A, B, C, and D to have shared cooldowns, then B/C/D should have sharesCooldownWith: A.

Just to clarify, the intention is that if A and B share a cooldown, B should reference A via sharesCooldownWith: A, but A should not reference B via sharesCooldownWith: B, because it would cause a circular-reference? This seems like an easy trap to fall into for sim implementers. Perhaps there is a better way to implement this that would prevent creating a footgun, possibly by using a hash of the shared cooldown abilities for the key instead.