Minor refactor of the login methods in tests.www.test_views (#10918)
Minor refactor of the login methods in tests.www.test_views (#10918)

- Instead of supporting only an Admin user in the base test class, you can also use a normal User or Viewer
- Only add users when they are being used so we can do a little less in the setup phase (minor speedup in TestDagACLView)
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