gcsim Optimizations

[srliao]

There are a couple things that can be further optimized:

• Get rid of goroutines currently used to block Eval from executing. The context switching is costing roughly 20% (https://discord.com/channels/845087716541595668/983391844631212112/996224294961020938)
• Refactor AttackEvent to split up the structure between variables that can be modified (and therefore needs to be cloned) and variables that can be kept the same to reduce the number of allocs

Additional possibilities??

• Event emitting??
• Task queue??