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
