chore: merge tests.AddFixtures and unittest.OverrideFixtures (#7648)

The only parameter that is ever used is a single directory, make it that only instead of a more complex option structure.

Remove tests.AddFixtures that was the simpler form because it is now redundant.

---

Backporting to v11.0 will help with automated backporting of bug fixes in need of custom made fixtures.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7648
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>

models/repo/repo_list_test.go

@@ -4,7 +4,6 @@
 package repo_test
 
 import (
-	"path/filepath"
 	"slices"
 	"strings"
 	"testing"
@@ -14,7 +13,6 @@ import (
 	"forgejo.org/models/unittest"
 	"forgejo.org/models/user"
 	"forgejo.org/modules/optional"
-	"forgejo.org/modules/setting"
 	"forgejo.org/modules/structs"
 
 	"github.com/stretchr/testify/assert"
@@ -410,13 +408,7 @@ func TestSearchRepositoryByTopicName(t *testing.T) {
 }
 
 func TestSearchRepositoryIDsByCondition(t *testing.T) {
-	defer unittest.OverrideFixtures(
-		unittest.FixturesOptions{
-			Dir:  filepath.Join(setting.AppWorkPath, "models/fixtures/"),
-			Base: setting.AppWorkPath,
-			Dirs: []string{"models/repo/TestSearchRepositoryIDsByCondition/"},
-		},
-	)()
+	defer unittest.OverrideFixtures("models/repo/TestSearchRepositoryIDsByCondition")()
 	require.NoError(t, unittest.PrepareTestDatabase())
 	// Sanity check of the database
 	limitedUser := unittest.AssertExistsAndLoadBean(t, &user.User{ID: 33, Visibility: structs.VisibleTypeLimited})