Improve Operator installation and add GKE features

⚠️ 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 (You are here)
• 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
• 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

⚠️

While using the Operator module to install it in a Cluster and switch between versions I wanted to improve a few things:

• Fetch the latest (semver sorted) tag from the project and use the manifests from that release so we don't have to continually support specific versions
• Set force_new and apply_only on the manifest provider, otherwise changing the version would have no effect, which wouldn't work if we want to update the version of the operator
• Export and fix the plumbing on a few variables/outputs that were necessary
• Export a runner_opts variable to reduce upkeep for other variables
• Add support for autoscaling and node taints for GKE

Closes #115 (closed)