Changes:

• Renames the system-managed usergroups as follows:
  • all-users becomes autogroup:users
  • all-members becomes autogroup:members
  • all-guests becomes autogroup:guests
• Verified that this change does not affect the security policies of any currently deployed project.

Contributes to #6578

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated
• Intend to cherry-pick into the release branch
• I'm proud of this work!