Why are these changes needed?

We shouldn't busy wait and use all those cycles just to wait for the next version. Instead we can use a condition variable and just check every second, and when notified of a change. This will also allow us to take a threadpool approach effectively afterwards instead of the current un-scaleable approach of creating a new thread for every channel.

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• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
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• Testing Strategy
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  • This PR is not tested :(