Add a registry logout functionality

[sepauli]

Is your feature request related to a problem? Please describe.

We have automated some tasks using scripts, including logging in to and interacting with an external registry.
The zarf tools registry login creates an entry with the authentication information in ~/.docker/config.json

After the tasks have completed, we would like to perform a logout so that the credentials are removed from ~/.docker/config.json, similar to docker registry logout registry.example.com

Describe the behavior you'd like

Add a zarf tools registry logout registry.example.com function, which removes the authentication information from ~/.docker/config.json