A way to access this stream is required if we wish to be able to toggle
profiling from fdbcli. There's two ways to do this:
1. Use `monitorLeader()` to get a `ClusterControllerFullInterface`, and use
`getWorkers` from there to get a list of `WorkerInterface`s, from which we can
access cpuProfilerRequest.
2. Move cpuProfilerRequest to ClientWorkerInterface and use the existing code
in the client that can fetch a list of all `ClientWorkerInterface`s.
The split between WorkerInterface and ClientWorkerInterface appears to be
what a client might have a need to call versus what is fdbserver-internal (and
thus no client should even want to call). Thus, it seems to make more sense to
acknowledge that profiling is useful to be able to toggle from a client, and go
with option (2).
Yichi Chiang