Move RepoTransfer from models to models/repo sub package

[lunny]

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.

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

[wxiaoguang]

Why? What's the benefit?

[lunny]

Why? What's the benefit?

I updated the description to explain the reason.

[wxiaoguang]

Why not totally decouple the repo & org models? Just use them from service packages?

[lunny]

Why not totally decouple the repo & org models? Just use them from service packages?

RepoTransfer now is at models, but if we want to move it into repo model, it will depend on Team, this is another reason why we need this change.
And we cannot move RepoTransfer to service layer.
Included moving RepoTransfer to models/repo sub package.

[lunny]

Last call for another review @go-gitea/technical-oversight-committee

[delvh]

Let's hope there aren't too many places relying on teams having potentially been loaded already (in terms of performance)