Add a logout option to the pinniped-auth plugin

[CapKenR]

Describe the feature request
Add the option to the pinniped-auth plugin to logout. Users need the ability to switch between credentials, i.e. between admin and non-admin credentials.

Describe alternative(s) you've considered
Right now the only option we've found is to delete the credentials and sessions caches in ~/.config/tanzu/pinniped/ and deleting the browser cache for the OIDC provider. We did find a proof of concept for this functionality in the Pinniped repository WIP: Proof of concept: client-side logout #1049.

Affected product area (please put an X in all that apply)

• ( ) APIs
• ( ) Addons
• (X) CLI
• (X) Docs
• (X) IAM
• ( ) Installation
• (X) Plugin
• (X) Security
• ( ) Test and Release
• (X) User Experience
• ( ) Developer Experience

Additional context

[github-actions]

Hey @CapKenR! Thanks for opening your first issue. We appreciate your contribution and welcome you to our community! We are glad to have you here and to have your input on Tanzu Framework.