Replace all calls to os.Remove/os.RemoveAll by retrying util.Remove/util.RemoveAll and remove circular dependencies from util.

Fix #12339

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: silverwind <me@silverwind.io>

* remove dependencys

* add missing fields

* CI.restart()

* Fix migration v96 to keep issue attachments

* Fix == operator

* delete attachments from the database and file system

* add migration

* fix import statements

* fix package name

* remove conditional should in case the confi has been changed and the server restarted

* simplify deletion of attachments in DB

* fix CI build

* fix review

* add copyright in the proper place

* fix review