Move migrating repository from frontend to backend (#6200)

Move migrating repository from frontend to backend (#6200)

* move migrating to backend

* add loading image when migrating and fix tests

* fix format

* fix lint

* add redis task queue support and improve docs

* add redis vendor

* fix vet

* add database migrations and fix app.ini sample

* add comments for task section on app.ini.sample

* Update models/migrations/v84.go

Co-Authored-By: lunny <xiaolunwen@gmail.com>
* Update models/repo.go

Co-Authored-By: lunny <xiaolunwen@gmail.com>
* move migrating to backend

* add loading image when migrating and fix tests

* fix fmt

* add redis task queue support and improve docs

* fix fixtures

* fix fixtures

* fix duplicate function on index.js

* fix tests

* rename repository statuses

* check if repository is being create when SSH request

* fix lint

* fix template

* some improvements

* fix template

* unified migrate options

* fix lint

* fix loading page

* refactor

* When gitea restart, don't restart the running tasks because we may have servel gitea instances, that may break the migration

* fix js

* Update models/repo.go

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>
* Update docs/content/doc/advanced/config-cheat-sheet.en-us.md

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>
* fix tests

* rename ErrTaskIsNotExist to ErrTaskDoesNotExist

* delete release after add one on tests to make it run happy

* fix tests

* fix tests

* improve codes

* fix lint

* fix lint

* fix migrations