Implement filters like they are displayed in the UI
Created by: eseliger
Currently, the changeset filters only allowed to filter by externalState, now they (almost) reflect what's in the UI.
almost
/ˈɔːlməʊst/
All states but reconcilerState: QUEUED
are correctly reflected. We need to think about a better API first to be able to query the "processing" changesets, because it's the joined set of queued and processing changesets.
Closes https://github.com/sourcegraph/sourcegraph/issues/13057