[ADR] GitLab Runner Sandbox image pulls

[Racer159]

Describe what should be investigated or refactored

We should ensure the decision to open up the gitlab-runner sandbox namespace is documented with its consequences so that impacted folks could reference it.

Links to any relevant code

uds-package-gitlab-runner/chart/templates/namespace.yaml

Line 7 in 18028e4

zarf.dev/agent: ignore

Additional context

This will have some downstream impacts we should layout (mostly to uds-core).