Improve dashboard's repo list performance (#18963)

* Improve dashboard's repo list performance

- Avoid a lot of database lookups for all the repo's, by adding a
undocumented "minimal" mode for this specific task, which returns the
data that's only needed by this list which doesn't require any database
lookups.
- Makes fetching these list faster.
- Less CPU overhead when a user visits home page.

* Refactor javascript code + fix Fork icon

- Use async in the function so we can use `await`.
- Remove `archivedFilter` check for count, as it doesn't make sense to
  show the count of repos when you can't even see them(as they are
  filited away).

* Add `count_only`

* Remove uncessary code

* Improve comment

Co-authored-by: delvh <dev.lh@web.de>

* Update web_src/js/components/DashboardRepoList.js

Co-authored-by: delvh <dev.lh@web.de>

* Update web_src/js/components/DashboardRepoList.js

Co-authored-by: delvh <dev.lh@web.de>

* By default apply minimal mode

* Remove `minimal` paramater

* Refactor count header

* Simplify init

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>

routers/api/v1/repo/repo.go

@@ -218,7 +218,6 @@ func Search(ctx *context.APIContext) {
 		}
 		results[i] = convert.ToRepo(repo, accessMode)
 	}
-
 	ctx.SetLinkHeader(int(count), opts.PageSize)
 	ctx.SetTotalCountHeader(count)
 	ctx.JSON(http.StatusOK, api.SearchResults{