Download CRDs from the repo

[oarribas]

As discussed in #121, create a command to download a set of CRDs from this repo (maybe omc pull crd?). That way, the omc could have an up-to-date list of common CRDs in case they are not included in the must-gather.

To not conflict with custom CRDs in ~/.omc/customresourcedefinitions/, maybe having 2 different directories there could help:

• ~/.omc/customresourcedefinitions/omc_base: where the above command will download the CRDs from this repo).
• ~/.omc/customresourcedefinitions/custom: for custom CRDs added by users. If this approach is used, when upgrading, the CRDs in ~/.omc/customresourcedefinitions/ should be moved to ~/.omc/customresourcedefinitions/custom.

If the two above directories are created, I think the omc_base should be checked before the custom one, or allow to configure the order with an option.

[bverschueren]

The CRD are available in an operator's bundle image [1] so perhaps we can figure out a way to extract it from there instead of duplicating those here and having to keep it in sync over time.

e.g.:

$ podman image save registry.redhat.io/rhosdt/jaeger-operator-bundle@sha256:<sha> |tar -xvf - <layer_id>.tar -O |tar -xvf - manifests/jaegertracing.io_jaegers.yaml -O|head -4
<layer_id>.tar
manifests/jaegertracing.io_jaegers.yaml
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  annotations:

[1] https://olm.operatorframework.io/docs/tasks/creating-operator-bundle/#operator-bundle