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.

routers/api/v1/repo/teams.go

@@ -42,7 +42,7 @@ func ListTeams(ctx *context.APIContext) {
 		return
 	}
 
-	teams, err := organization.GetRepoTeams(ctx, ctx.Repo.Repository)
+	teams, err := organization.GetRepoTeams(ctx, ctx.Repo.Repository.OwnerID, ctx.Repo.Repository.ID)
 	if err != nil {
 		ctx.InternalServerError(err)
 		return