User specific repoID or xorm builder conditions for issue search (#19475)

* extend models.IssuesOptions to have more specific repo filter options

* use new options

* unrelated refactor

* rm RepoIDs

services/migrations/gitea_uploader_test.go

@@ -105,7 +105,7 @@ func TestGiteaUploadRepo(t *testing.T) {
 	assert.Len(t, releases, 1)
 
 	issues, err := models.Issues(&models.IssuesOptions{
-		RepoIDs:  []int64{repo.ID},
+		RepoID:   repo.ID,
 		IsPull:   util.OptionalBoolFalse,
 		SortType: "oldest",
 	})