Load all `briefs_search_filters` for DOS
Load all `briefs_search_filters` for DOS

If we only load the filters for the latest live framework, the search
will break when we flip DOS3 to live. We can use `try_load_manifest` and
load filters for all DOS frameworks (DOS1 doesn't have this manifest).

alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend