Regions cache should only be filled for regional commands

[EtienneM]

And the --password-only flag is broken
And the help tries to login

This is because of this piece of code: https://github.com/Scalingo/cli/blob/master/cmd/commands.go#L32-L38

Before running any command, we fill the regions cache which requires to be logged in. And the call to session.Login do not use any flag on the command line.

[EtienneM]

We should fill the regions cache only for regional commands

[EtienneM]

Related to https://app.intercom.io/a/apps/w4oogu7s/inbox/inbox/conversation/22870997936#part_id=comment-22870997936-3400397128

This is because the user deleted the Scalingo token from his profile (https://my.agora-fr1.scalingo.com/profile). Then nothing works anymore :'(

To prevent that, we should be able to run scalingo logout && scalingo login. And this is achieved by only filling the cache for regional commands