Reimplement GetUserOrgsList to make it simple and clear (#32486)

Reimplement GetUserOrgsList and also move some functions and test to
org_list file.

---------

Co-authored-by: Zettat123 <zettat123@gmail.com>

services/oauth2_provider/access_token.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	auth "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
 	org_model "code.gitea.io/gitea/models/organization"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/log"
@@ -192,7 +193,10 @@ func NewAccessTokenResponse(ctx context.Context, grant *auth.OAuth2Grant, server
 // returns a list of "org" and "org:team" strings,
 // that the given user is a part of.
 func GetOAuthGroupsForUser(ctx context.Context, user *user_model.User) ([]string, error) {
-	orgs, err := org_model.GetUserOrgsList(ctx, user)
+	orgs, err := db.Find[org_model.Organization](ctx, org_model.FindOrgOptions{
+		UserID:         user.ID,
+		IncludePrivate: true,
+	})
 	if err != nil {
 		return nil, fmt.Errorf("GetUserOrgList: %w", err)
 	}