Decouple unit test, remove intermediate unittestbridge package (#17662)

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

integrations/api_org_test.go

@@ -11,7 +11,7 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/models"
-	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 
@@ -44,7 +44,7 @@ func TestAPIOrgCreate(t *testing.T) {
 		assert.Equal(t, org.Location, apiOrg.Location)
 		assert.Equal(t, org.Visibility, apiOrg.Visibility)
 
-		db.AssertExistsAndLoadBean(t, &models.User{
+		unittest.AssertExistsAndLoadBean(t, &models.User{
 			Name:      org.UserName,
 			LowerName: strings.ToLower(org.UserName),
 			FullName:  org.FullName,