search: populate Stats.Repos before applying display limit
Created by: keegancsmith
Our stats should be calculated before applying the display limit. IE stats should be based on the match limit (count:). This moves the calculation of Repos to before we apply the display limit. Additionally it now lives inside of the progress agreggator rather than in the http handler, which is more appropriate.
Depends on https://github.com/sourcegraph/sourcegraph/pull/27903
Part of https://github.com/sourcegraph/sourcegraph/pull/27903