Add ability to ensure a specified connection.

[martinlingstuyl]

Currently, when using login --ensure, the CLI ensures the active connection. However, if we use the --connectionName option, it would be better if it would ensure the specified connection. It currently does not do that.

Let's fix this.

Running the following command:

m365 login --ensure --connectionName "some-name"

...should ensure that the specified connection is not expired and kickstart the login process if it is.
If the connectionName is not available, it means it's a new connection anyway, and the login process must start as well,