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/context/repo.go

@@ -14,7 +14,6 @@ import (
 	"path"
 	"strings"
 
-	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/models/db"
 	git_model "code.gitea.io/gitea/models/git"
 	issues_model "code.gitea.io/gitea/models/issues"
@@ -709,7 +708,7 @@ func RepoAssignment(ctx *Context) context.CancelFunc {
 	ctx.Data["PullRequestCtx"] = ctx.Repo.PullRequest
 
 	if ctx.Repo.Repository.Status == repo_model.RepositoryPendingTransfer {
-		repoTransfer, err := models.GetPendingRepositoryTransfer(ctx, ctx.Repo.Repository)
+		repoTransfer, err := repo_model.GetPendingRepositoryTransfer(ctx, ctx.Repo.Repository)
 		if err != nil {
 			ctx.ServerError("GetPendingRepositoryTransfer", err)
 			return cancel