Allow deploying multiple runners in a single k8s cluster

⚠️ This MR is based on Remove test dirs and flatten operator modules (!146 - merged) • Georgi N. Georgiev | GitLab • 17.10

⚠️ This MR is part of a series:

• Migrate Kubernetes integration tests to use the... (gitlab-org/gitlab-runner!5175 - merged) • Georgi N. Georgiev | GitLab • 17.7
• Improve Operator installation and add GKE features (!124 - merged) • Georgi N. Georgiev | GitLab • 17.10
• https://gitlab.com/gitlab-org/ci-cd/runner-tools/runner-kubernetes-infra/-/merge_requests/1+s
• Remove test dirs and flatten operator modules (!146 - merged) • Georgi N. Georgiev | GitLab • 17.10
• Allow deploying multiple runners in a single k8... (!147 - merged) • Georgi N. Georgiev | GitLab • 18.1 (You are here)
• https://gitlab.com/gitlab-org/ci-cd/runner-tools/runner-kubernetes-infra/-/merge_requests/2+s
• Run CI jobs in kubernetes (gitlab-org/charts/gitlab-runner!504 - merged) • Georgi N. Georgiev | GitLab • 17.9

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Related to [K8S Dogfooding] Extend GRIT to allow for more ... (#129 - closed) • Georgi N. Georgiev | GitLab • 18.2