Adding multi-arch image support for `arm64` and `amd64`. This uses dockers new `buildx` feature, to enable further architectures more work will be required to update the `runner/Dockerfile` file to pull architecture-specific releases.
The Makefile targets really should only be used for local testing and not for release, additional work to appropriately tag the release images may need to be added but for now, I've not added that logic.
Fixes: #86
Signed-off-by: Michael Fornaro <20387402+xUnholy@users.noreply.github.com>
RunnerSet is basically ReplicaSet for Runners.
It is responsible for maintaining number of runners to match the desired one. That is, it creates missing runners from `.Spec.Template` and deletes redundant runners.
Similar to ReplicaSet, this does not support rolling update of runners on its own. We might want to later add `RunnerDeployment` for that. But that's another story.
