Support explicit session token as env var for `up org token`

[RedbackThomson]

What problem are you facing?

up org token currently relies on pulling the session token from the selected profile, which requires a prior step of logging in using up login. For some systems, where up is running inside a container, it would be simpler to pass that session token directly to the command as an env var which would take precedence over loading from the profile.

How could Upbound help solve your problem?

I would expect it to look something like:

UP_TOKEN=<redacted> up org token