Following up on #8362, #7116, and #8361.

We've recently reached a major milestone in provisioning the infrastructure that will support Spack's upcoming automated release and PR testing process. In addition to providing several new services, we've also taken the opportunity to migrate service for the main spack.io website to the same infrastructure, consolidating in a single deployment. At the present, we are hosting the following services:

• www.spack.io: the main Spack website.
• gitlab.spack.io: the Gitlab instance that will power Spack's custom pipelines. These pipelines will build, test, sign, and upload pre-compiled binaries for several of the most popular Spack packages.
• cdash.spack.io: the CDash instance that will ingest, aggregate, and present data on the results of the above pipelines. We'll be able to use this resource to quickly identify packages that are not building successfully and determine what changes are likely to address any issues that prevent their successful build.
• k8s.spack.io: dashboard app for administrators of the kubernetes cluster that powers all these services.

There are a few minor matters that still need to be addressed. This issue will track them.

• The Gitlab instance is still running on Gitlab Community Edition. We still need to secure a license for ultimate edition and migrate.
• The CDash instance is running, but does not seem to be working quite right. We'll need to investigate and fix any issues in the recently provided kitware/cdash docker container.
• Move resource definitions from spack/testing-sandbox to a more permanent home.