Validate user input during configuration phase

[sgoings]

In the configure phase, we want to make sure that the user is providing the right type of input and failing fast if possible to provide the user a chance to retry answering a prompt.

@bacongobbler explains:

The "please choose a release" from rigger configure was confusing. I thought it would equate to a deisctl config platform set version=v1.10.0, but instead it attempts to check out that branch (which it won’t error out if the branch isn’t found on rigger provision which makes sense, but it should fail if rigger can’t check out that branch IMO