Add output file to ziti agent controller snapshot-db command

[emoscardini]

The current command ziti agent controller snapshot-db generates a file names based on a timestamp, but that timestamp is based on when is successfully completes the snapshot & so is unpredictable.

Example: you issue the command on 20230104-062503, but the output file can be different depending on how long it takes to take the snapshot, so the output file can be 20230104-062503+n(number of minutes it can take), so you end up with 20230104-062805(took 3 minutes)

It would be nice to add a --output so you can specify the name of the file AND/OR have the output of the command return the file name instead of just "success"