feat(projects): start storing ID on project credentials

[rektdeckard]

https://linear.app/livekit/issue/DPRO-461/save-project-id-in-cli-credentials

• Begins saving project ID on credentials when authenticating
• Adds ability to specify a specific project to auth with lk cloud auth <project_id>, which when backend support is added, will let us pre-select (and automatically confirm) project to authenticate.

[rektdeckard]

@yoonsio we don't backfill existing configured projects, just new auths from now on. If you want I can add a check and backfill if any project doesn't have an ID whenever config file is read? But we need new API for it.