PR summary

Closes #314 (finally).

This fixes a performance issue where the future executor eats up all available CPU cycles because we naively called waker.wake() in our futures' poll functions.

These changes align future waking with the redux loop, i.e. state mutations. The redux thread stores a map of wakers (of all active futures) and calls wake() on each after an action got reduced.

Futures register their waker by sending it over a channel they got in via the context.

testing/benchmarking notes

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followups

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changelog

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- summary of change [PR#1234](https://github.com/holochain/holochain-rust/pull/1234)

documentation

• this code has been documented according to our docs checklist