API: Restrict anonymous user information access (#18422)

Existing /api/alert-notifications now requires at least editor access.
Existing /api/alert-notifiers now requires at least editor access.
New /api/alert-notifications/lookup returns less information than
/api/alert-notifications and can be access by any authenticated user.
Existing /api/org/users now requires org admin role.
New /api/org/users/lookup returns less information than
/api/org/users and can be access by users that are org admins,
admin in any folder or admin of any team.
UserPicker component now uses /api/org/users/lookup instead
of /api/org/users.

Fixes #17318

public/app/plugins/panel/gettingstarted/GettingStarted.tsx

@@ -79,7 +79,7 @@ export class GettingStarted extends PureComponent<PanelProps, State> {
         href: 'org/users?gettingstarted',
         check: () => {
           return getBackendSrv()
-            .get('/api/org/users')
+            .get('/api/org/users/lookup')
             .then((res: any) => {
               return res.length > 1;
             });