Feature: support `login` option

[ProfFrnswrth]

With a new logout being performed at the end of a CI job it would be nice to have a login option that can be passed. We have a use case where we connect to multiple tailnets in a single workflow. Historically we have removed the binary completely from the runner and reinstalling the binary but it would be nice to just be able to login w/ a different set of OAuth credentials.