Show help text on instance location

[edlerd]

Done

• Show help text on instance location to direct user how to start a migration
• Improve labels in instance configuration
• User "cluster member" as label instead of "location" consistently
• fix cluster group selector styling

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @mas-who or @edlerd for access.
   • With a local copy of this branch, build and run as described in the docs.
2. Perform the following QA steps:
   • Check the instance location field in the instance configuration on the instance detail page. Ensure the help text works to guide the user.

[webteam-app]

Demo

Jenkins

demos.haus

[mas-who]

QA looks good, small copy suggestion.

[mas-who]

LGTM, thanks for the changes 👍