Wake up threads more aggressively if there is known work to do

[james7132]

Upon investigating https://github.com/bevyengine/bevy/issues/6941, we've found that thread wakeup times have been a significant bottleneck when spinning up large batches of tasks, like those mentioned in #91.

Would it be possible to more aggressively wake up threads (i.e. 2+ at a time), if and only if we know there is sufficient work for all of them? Whenever a thread is stealing work from another, it has an approximation of how much remaining work is in both threads, so it may be reasonable to weigh the potential contention against the cost of sequentially context switches as threads wake up.