feat: change pool noodle to use channels to prevent spamming pop

[sprutton1]

After a conversation with @fnichol we decided it would be better to use channels to pass work around here so we aren't hammering pop() in a bunch of threads and are instead just polling for work. We should be just as fast (if not faster) under load, but we'll be a lot quieter when sitting still. We limit total threads using a semaphore so we will block work until new slots appear.

[sprutton1]

/try

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/try

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/try

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/try

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/try

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/try

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/try