Add missing `Delete user and contributions` action in admin user view

📖 What does this MR do?

Related to #337156 (closed)

In !64648 (merged) we moved the admin user actions from cards to a User administration dropdown. This caused a regression where the Delete user and contributions action doesn't show up for users that are the sole owner of a group. As I was investigating this regression I noticed the path for the Delete user and contributions actions was actually incorrect (missing the hard_delete=true query string) so this MR also fixes that issue.

📷 Screenshots

Before	After

💻 How to setup and validate locally

1. Navigate to /admin/users
2. Choose a user
3. Click Impersonate in the upper right corner
4. Create a group
5. Click Stop impersonation in the upper right corner
6. Click the User administration dropdown

🚦 Does this MR meet the acceptance criteria?

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