Add a new gitlab:users:clear_all_authentication_tokens task

What does this MR do?

It adds a new gitlab:users:clear_all_authentication_tokens task that clear all the users' authentication tokens.

Are there points in the code the reviewer needs to double check?

I've chosen the simplest approach possible, as suggested by @jacobvosmaer-gitlab and @yorickpeterse in https://gitlab.com/gitlab-org/gitlab-ce/issues/22537#note_16528989.

Why was this MR needed?

We will need it to provide proper mitigation steps for #22537 (closed).

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Part of #22537 (closed).