Dashboards: hide playlist edit functionality from viewers and snapshots link from unauthenticated users (#28992)

* feat: hide snapshots menu item from viewers

* feat(playlists): prevent viewers from creating/editing playlists

* feat: prevent viewers seeing playlist nav link if no playlists

* refactor(playlist): rename isViewer property to canEditPlaylists

* revert(playlists): put back note if viewer and no playlists

* refactor(snapshots): consider admin/editor permission in folders/dashboards for displaying menu item

* feat(snapshots): only show snapshot nav item if user is signed in

* fix(snapshots): revert snapshots to previous state if delete snapshot api error