[MODERATION] Add repo transfers to blocked functionality (squash)

- When someone gets blocked, remove all pending repository transfers
from the blocked user to the doer.
- Do not allow to start transferring repositories to the doer as blocked user.
- Added unit testing.
- Added integration testing.

(cherry picked from commit 8a3caac330)
(cherry picked from commit a92b4cfeb6)
(cherry picked from commit acaaaf07d9)
(cherry picked from commit 735818863c)
(cherry picked from commit f50fa43b32)
(cherry picked from commit e166836433)
(cherry picked from commit 82a0e4a381)

services/repository/transfer.go

@@ -85,6 +85,10 @@ func ChangeRepositoryName(ctx context.Context, doer *user_model.User, repo *repo
 // StartRepositoryTransfer transfer a repo from one owner to a new one.
 // it make repository into pending transfer state, if doer can not create repo for new owner.
 func StartRepositoryTransfer(ctx context.Context, doer, newOwner *user_model.User, repo *repo_model.Repository, teams []*organization.Team) error {
+	if user_model.IsBlocked(ctx, newOwner.ID, doer.ID) {
+		return user_model.ErrBlockedByUser
+	}
+
 	if err := models.TestRepositoryReadyForTransfer(repo.Status); err != nil {
 		return err
 	}