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.

models/organization/team.go

@@ -11,7 +11,6 @@ import (
 
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/perm"
-	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/log"
@@ -78,9 +77,8 @@ type Team struct {
 	LowerName               string
 	Name                    string
 	Description             string
-	AccessMode              perm.AccessMode          `xorm:"'authorize'"`
-	Repos                   []*repo_model.Repository `xorm:"-"`
-	Members                 []*user_model.User       `xorm:"-"`
+	AccessMode              perm.AccessMode    `xorm:"'authorize'"`
+	Members                 []*user_model.User `xorm:"-"`
 	NumRepos                int
 	NumMembers              int
 	Units                   []*TeamUnit `xorm:"-"`
@@ -155,17 +153,6 @@ func (t *Team) IsMember(ctx context.Context, userID int64) bool {
 	return isMember
 }
 
-// LoadRepositories returns paginated repositories in team of organization.
-func (t *Team) LoadRepositories(ctx context.Context) (err error) {
-	if t.Repos != nil {
-		return nil
-	}
-	t.Repos, err = GetTeamRepositories(ctx, &SearchTeamRepoOptions{
-		TeamID: t.ID,
-	})
-	return err
-}
-
 // LoadMembers returns paginated members in team of organization.
 func (t *Team) LoadMembers(ctx context.Context) (err error) {
 	t.Members, err = GetTeamMembers(ctx, &SearchMembersOptions{