dlevy-msft-sql changed the title Implement :perftrace command Implement :perftrace and :help commands

dlevy-msft-sql changed the title Implement :perftrace and :help commands feat: implement :perftrace and :help commands

:perftrace redirects timing/statistics output to a file, stderr, or stdout.
:help displays the list of available sqlcmd commands with usage.

Both commands validate arguments and return appropriate errors.