worker.Options.WorkerActivitiesPerSecond applies after poll is received

[cretz]

Expected Behavior

Since this rate limit is applied post-poll-pre-process, server timeouts apply while it is waiting. We even have a doc on this field saying users can set it to a fraction of a second, e.g. 1 activity every 10s, but if they had a heartbeat timeout, it could timeout before it starts.

We should either fix this (hard) or at least document this warning on the field.