Search on group member list UI

There is currently no way to search for a member in a group, using the group member list view (XWiki.XWikiGroupSheet). We cannot use the browser search either, since the rows are loaded through AJAX.
The only way to actually search would be to use the object editor + browser text search, but for very large groups, the page does not even seem to load (c.f XWIki.XWikiAllGroup on www.xwiki.org).

A AJAX filter should be implemented on the XWiki.XWikiGroupSheet UI, which would act as a search.