Use an existing session token when connecting to a Coder deployment

[sharkymark]

To connect to a Coder deployment, the Coder plugin opens the Coder UI and issues another session token aka API key.

As a user, I want to use a longer-life token that I created with the Coder CLI.

So the UI should let a user enter an existing session token and not got to the Coder UI.

I propose a checkbox 'Use existing session token' or API key, to be consistent

When checked, the session token pop-up will appear after the Connect button is pressed.