Use db.ListOptions directly instead of Paginator interface to make iteasier to use and fix performance of /pulls and /issues (#29990) (#30447)

backport #29990

This PR uses `db.ListOptions` instead of `Paginor` to make the code
simpler.
And it also fixed the performance problem when viewing /pulls or
/issues. Before the counting in fact will also do the search.

Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: silverwind <me@silverwind.io>

modules/indexer/issues/internal/model.go

@@ -104,7 +104,7 @@ type SearchOptions struct {
 	UpdatedAfterUnix  *int64
 	UpdatedBeforeUnix *int64
 
-	db.Paginator
+	Paginator *db.ListOptions
 
 	SortBy SortBy // sort by field
 }