Move RepoTransfer from models to models/repo sub package (#32506)

`RepoTransfer` now is at models, but if we want to move it into `repo`
model, it will depend on `Team`. So this PR also makes repo model depend
on org model to make it possible. Just refactor, no code change.

- [x] Move `DeleteOrganization` from `models/organization` to service
layer
- [x] Move `AccessibleTeamReposEnv` to `models/repo`
- [x] Move `RepoTransfer` from `models` to `models/repo`
- [x] Merge `getUserTeamIDs` and `GetUserTeamIDs`, Merge `GetUserTeams`
and `getUserTeams`.
- [x] Remove `Team`'s `Repos []*repo_model.Repository` to avoid dependency recycle.

services/convert/repository.go

@@ -7,7 +7,6 @@ import (
 	"context"
 	"time"
 
-	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/perm"
 	access_model "code.gitea.io/gitea/models/perm/access"
@@ -158,8 +157,8 @@ func innerToRepo(ctx context.Context, repo *repo_model.Repository, permissionInR
 
 	var transfer *api.RepoTransfer
 	if repo.Status == repo_model.RepositoryPendingTransfer {
-		t, err := models.GetPendingRepositoryTransfer(ctx, repo)
-		if err != nil && !models.IsErrNoPendingTransfer(err) {
+		t, err := repo_model.GetPendingRepositoryTransfer(ctx, repo)
+		if err != nil && !repo_model.IsErrNoPendingTransfer(err) {
 			log.Warn("GetPendingRepositoryTransfer: %v", err)
 		} else {
 			if err := t.LoadAttributes(ctx); err != nil {
@@ -248,7 +247,7 @@ func innerToRepo(ctx context.Context, repo *repo_model.Repository, permissionInR
 }
 
 // ToRepoTransfer convert a models.RepoTransfer to a structs.RepeTransfer
-func ToRepoTransfer(ctx context.Context, t *models.RepoTransfer) *api.RepoTransfer {
+func ToRepoTransfer(ctx context.Context, t *repo_model.RepoTransfer) *api.RepoTransfer {
 	teams, _ := ToTeams(ctx, t.Teams, false)
 
 	return &api.RepoTransfer{