3.0.0-rc.1

This is a major release for kube-applier, redesigning the internals to work with kubernetes Custom Resources.

On a high level:

• A new CRD is introduced, Waybill: it defines the source of manifest files as well as options related to applying them (these were mostly defined as namespace annotations previously)
• There are no more "batch" runs. Each Waybill (which corresponds to a namespace) is applied independently of others.
• Run results are captured in the status subresource and is accessible with kubectl.
• Improved logs and metrics.
• Tests are not using mock interfaces anymore but build on the envtest package and run against a local apiserver.
• More flexible integration with strongbox for encrypted file support per namespace.
• Improved performance (faster runs, lower resources on average)