Security and safety improvements for gitlab-workhorse integration

Companion to https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/60

- Use a custom content type when sending data to gitlab-workhorse
- Verify (using JWT and a shared secret on disk) that internal API requests came from gitlab-workhorse

This will allow us to build features in gitlab-workhorse that require
more trust, and protect us against programming mistakes in the future.

This is designed so that no action is required for installations from
source. For omnibus-gitlab we need to add code that manages the shared
secret.

See merge request !5907

Change update interval of runners when trying to preserve contacted_at

See merge request !6126

Pass dependencies to CI configuration nodes

## What does this MR do?

This MR makes it possible to pass dependencies to CI configuration nodes.

## What are the relevant issue numbers?

See #15060

## Does this MR meet the acceptance criteria?

- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

See merge request !6009