performance pass

[halfcyan]

i just wanted to do a larger pass of everything performance-wise since small improvements add up in a system like this

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[halfcyan]

added the benchmarking stuff to see how much this improves stuff and uh. wow.

VM count	Before: full scan	After: delta construction	Approx. speedup
10	116 µs	51 µs	2.3x
100	752 µs	41 µs	18.4x
1,000	5.91 ms	42 µs	140x
10,000	57.83 ms	41 µs	1,412x
100,000	567.92 ms	41 µs	13,795x

[halfcyan]

the biggest thing is that the heartbeat resource calc changed from O(VMs) to O(1) which is massive

[TheHeroBrine422]

Overall I like the ideas, but there are minor issues.

On top of this, scheduler_actor.rs is getting really hard to follow. We need better documentation and/or to split the module into several parts.

@korewaChino should likely review the ch_driver changes since I am not super familar with that section of the codebase, although it looks fine to me.