[DT table] Show different empty states when there are no groups and no source

• Show "Session expired" when there are no groups and no source
• Show "No groups" only when there are no groups

References

Issue: #553044 (closed)

UX Paper Cuts Planning issue: #513103 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Go to http://gdk.test:3000/groups/new#import-group-pane
2. Choose direct transfer. You can use https://gitlab.com and you personal access token (you can create it https://gitlab.com/-/user_settings/personal_access_tokens?page=1&state=active&sort=expires_asc)
3. Leave this tab open for a few hours, or replace this condition with true

MR acceptance checklist

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