feat: Add option to hide help text at the end #308

It can be a little confusing when running stackablectl within scripts. The help text can look like a command didn't run correctly, when it did and the help text is suggesting what to do next:

We could either add an option to disable the help text, or just hide it if CI=true (which we can then export in the getting_started.sh scripts).

For reference, Terraform uses an env var TF_IN_AUTOMATION to control the help text output.