Implement unauthenticated logic for /v2/service_plans and /v2/services

This commit was initially reverted as part of the attempt to reduce CC
flakes. We've cherry-picked this commit back in and run the tests.
Everything looks fine, so we're putting the commit back in.
Added service guid in service plans response for unauthenticated users

- added visibility filter for unauthenticated access
- serivce guid no longer filtered out for unauth users
- added tests that verify that unauth users can list the services and
  public service plans

[#70028330]