Migrate to gitlab.tpo

Steps to start doing reviews of sbws to gitlab.tpo:

• create sbws repository that will be used by the MR, either in the gitlab root or network healt team
• clone our personal repositories from the previous one
• #40007 (closed): create a .gitlab-ci.yml similar to .travis.yml, so that the sbws can be automatically tested Blocked until we have Gitlab runners. For now we are still using Travis.

Steps to migrate completely to gitlab.tpo:

• migrate Trac tickets
• migrate Trac wiki page about sbws. @gaba is working on this
• migrate GitHub issues. Would be great to do it automatically. We were doing it manually in #28589 (closed)
• #40001 (closed): change references to Trac in the documentation
• #40002 (closed): change the references to git.tpo in the documentation

It would also be great:

• migrate GitHub PRs to Gitlab MRs. Only if not much work to have an script to do it automatically