Add debug and must-gather container images to release mirror tasks

[johnsimcall]

It is convenient to be able to "oc debug node/nodeName" in order to login to the node and debug issues. The container image required for this command to succeed is not mirrored by default. Let's create a task that will mirror the registry.redhat.io/rhel7/support-tools image. This may also require modifying the /etc/containers/registries.conf file to rewrite those image pull requests to use an alternate registry. Instead of creating a machineConfig to update registries.conf, a user can manually specify the debug image to use like this, oc debug node/nodeName --image myregistry.example.com/whatever/support-tools:latest

We should also mirror the quay.io/openshift/origin-must-gather:latest image ...

1 - Using oc debug node in disconnected clusters
2 - [disconnected] 'registry.redhat.io/rhel7/support-tools' image is being pulled when running oc debug node/xxx in disconnected install.
3 - Collecting must-gather in a Disconnected Environment

[johnsimcall]

It appears that must-gather may have made it into oc adm release mirror
Check like this:

$ oc adm release info | grep must-gather
  must-gather            sha256:f1ffcdcbd684afd61ff1874b47e1c61a0f7adab93b7a21123a1e29b041d3dabf