go/cmd: Implement vttestserver
go/cmd: Implement vttestserver

vttestserver is the Go version of `run_local_server.py`, and follows a
similar interface.

Most notably:

- All the commandline flags have the same names, but they're implemented
as Golang flags, so they only take a single dash
- The JSON output to stdout, and process control through stdin should be
identical

alainjobart/vitess,mattharden/vitess,mahak/vitess,tinyspeck/vitess,tinyspeck/vitess,HubSpot/vitess,sougou/vitess,tirsen/vitess,enisoc/vitess,alainjobart/vitess,sougou/vitess,mahak/vitess,davygeek/vitess,mattharden/vitess,tinyspeck/vitess,tinyspeck/vitess,dcadevil/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,mahak/vitess,sougou/vitess,tirsen/vitess,enisoc/vitess,alainjobart/vitess,sougou/vitess,mattharden/vitess,vitessio/vitess,enisoc/vitess,mattharden/vitess,mattharden/vitess,davygeek/vitess,HubSpot/vitess,HubSpot/vitess,dcadevil/vitess,alainjobart/vitess,HubSpot/vitess,enisoc/vitess,HubSpot/vitess,enisoc/vitess,vitessio/vitess,mattharden/vitess,sougou/vitess,sougou/vitess,mattharden/vitess,enisoc/vitess,davygeek/vitess,dcadevil/vitess,dcadevil/vitess,alainjobart/vitess,mattharden/vitess,mahak/vitess,sougou/vitess,davygeek/vitess,tinyspeck/vitess,alainjobart/vitess,HubSpot/vitess,davygeek/vitess,tirsen/vitess,alainjobart/vitess,dcadevil/vitess,vitessio/vitess,davygeek/vitess,tinyspeck/vitess,tirsen/vitess,davygeek/vitess,vitessio/vitess,vitessio/vitess,enisoc/vitess,HubSpot/vitess,tirsen/vitess,tinyspeck/vitess,tirsen/vitess,vitessio/vitess,HubSpot/vitess,dcadevil/vitess,vitessio/vitess,tirsen/vitess,alainjobart/vitess,sougou/vitess,tirsen/vitess,mahak/vitess,mahak/vitess,tirsen/vitess,dcadevil/vitess,mattharden/vitess,mattharden/vitess