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.

templates/org/team/repositories.tmpl

@@ -27,7 +27,7 @@
 				{{end}}
 				<div class="ui{{if not $canAddRemove}} top{{end}} attached segment">
 					<div class="flex-list">
-						{{range .Team.Repos}}
+						{{range $.TeamRepos}}
 							<div class="flex-item tw-items-center">
 								<div class="flex-item-leading">
 									{{template "repo/icon" .}}