More parallel proxy and new services
Increase parallelism on the proxy to be completely non-blocking per stream.
In the past requesting N new streams but having one of those streams block on a timeout would backup everything for a minimum of 20s (the default connection timeout). If the overall timeout wasn't that long no work could get done. Now the proxy returns immediately on a new stream request and does all connection work asynchronously. It may still block if client streaming (i.e. Localfile.Write) gets too far ahead of connected clients but as most RPCs are unary this generally isn't a problem.
Link in channelz support so it can be queried if desired.
Remove flag definitions in packages and export vars instead. Then rebind in package main for the commands.
NOTE: Implementors with their own versions of the server/CLI will need to bind the flags to have them work again.
Rework how servers start so it's easy/possible for others to add their owner interceptors to the server. This allows metrics/tracing linkage without forcing a specific implementation.
Add FDB service implementing support for wrapping fdbcli and a definition for editing the config file remotely as well (implementation in next release).
Add rm support in localfile (as Remove)
Minor documentation and CLI cleanups for clarity