This adds a command-line tool named `gvisor_k8s_tool` that allows running the
`runsc` installer image as a DaemonSet in a Kubernetes cluster, either through
GKE or through `kubectl` configuration.
Example:
```shell
# Install using default kubectl context:
$ ./gvisor_k8s_tool install --cluster=kube: --image=my-runsc-installer
# Install using custom kubectl config and context:
$ KUBECONFIG=/tmp/myconfig ./gvisor_k8s_tool \
install --cluster=kube:mycontext --image=my-runsc-installer
# Install in a GKE cluster:
$ ./gvisor_k8s_tool install \
--cluster=gke:projects/myproject/locations/us-central1-a/clusters/mylittlecluster \
--image=my-runsc-installer
```
PiperOrigin-RevId: 557945316
Also make `runsc debug` write to stdout and log file to make it
easier to see the output when running the command manually.
PiperOrigin-RevId: 470042053
