Currently, v2spa's alerts-controls allow users to query for alerts EITHER by sheriff OR bug OR report. This causes alerts-section to issue multiple parallel /api/alerts requests and merge the results, which is a bit complex and confusing, and probably not what users really want.

There are reports of users wishing to filter by both bug AND sheriff:
https://github.com/catapult-project/catapult/issues/3205

Let's simplify alerts-controls and alerts-section to fetch and display a single alerts query. Empty alerts-controls should allow users to enter EITHER a sheriff OR bug OR report OR revision range at first, then click a filter icon for a menu to add filters. If users want to view all alerts for a sheriff rotation plus all alerts for a bug on the same page, they can already add multiple alerts-sections.