[CLI Improvements] add validations for command's flags and arguments

[schoren]

Commands have a well defined set of flags and/or arguments, and what they should look like.

We currently validate one parameter at a time, so if a user has 2 incorrect parameters, they need to run the command once, see the 1st error, fix it. Run the command again, see the 2nd error, fix it. Run the command again.

We can validate the entire command parameters at once, and show all errors at once, so the user doesn't need to do multiple retries for the same command.