Adding multi-platform support for linux/amd64 and linux/arm64

[cin]

Still needs testing as I'm sure I've left something out.

Resolves #81

[cin]

I think this is working, but I don't have a good way of testing the arm images. I've tried building images on a few different configurations as well. I'm using Rancher Desktop on a 2018 Intel based mac, podman on a 2021 m1 mac, and Docker Desktop on WSL under windows. The only issue I'm having is with the images produced by podman. It doesn't have arm64 and amd64 manifests in the image.

# built under WSL with Docker Desktop on Windows 11
❯ docker buildx imagetools inspect us.icr.io/icm-docker-images/varnish-operator:wsl-support
Name:      us.icr.io/icm-docker-images/varnish-operator:wsl-support
MediaType: application/vnd.docker.distribution.manifest.list.v2+json
Digest:    sha256:555238d753bee3066abdf52e76927ea28294b3ad0cd35ad61b54c6e2df7bc4d4

Manifests:
  Name:      us.icr.io/icm-docker-images/varnish-operator:wsl-support@sha256:38de421069d3899c00ca9e04026dedc017596a36d83fd6c2e117543da735fa67
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/amd64

  Name:      us.icr.io/icm-docker-images/varnish-operator:wsl-support@sha256:105e783c9c3200ce16e63e66cfaf2ec9969af36f3553b8fdb8eca28a767c452b
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/arm64

# built on x86 mac w/Rancher Desktop as Docker Desktop replacement
❯ docker buildx imagetools inspect us.icr.io/icm-docker-images/varnish-operator:arm-support
Name:      us.icr.io/icm-docker-images/varnish-operator:arm-support
MediaType: application/vnd.docker.distribution.manifest.list.v2+json
Digest:    sha256:bd39b9d54fa6ccb46cb57bbc2e9c7368cc67eef182a8fc2c87bc15196d2ec9c0

Manifests:
  Name:      us.icr.io/icm-docker-images/varnish-operator:arm-support@sha256:3174538fe2ca304f658ae11d2057739ae7880d4235da4368c52ed25db69e1870
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/arm64

  Name:      us.icr.io/icm-docker-images/varnish-operator:arm-support@sha256:91713a00743b47c194580494a25fefcfd80937b9cc6b385e85e3e49c8304b08a
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/amd64

# built on m1 mac with podman
❯ docker buildx imagetools inspect us.icr.io/icm-docker-images/varnish-operator:m1-arm
Name:      us.icr.io/icm-docker-images/varnish-operator:m1-arm
MediaType: application/vnd.oci.image.manifest.v1+json
Digest:    sha256:3ac3ff69aee695fe6a516e676b32aabcf3d393bdcf8a2300fb99306d1bbb69fa

I think the only way I will know if the build works under GHA is to merge/tag it. I'm also having issues on the m1 mac with the e2e-tests. The create script is failing to load the images onto the kind cluster's nodes. This happens with the other images as well, so it's not just an issue with the podman produced images. The e2e-tests work fine under WSL and my old mac.

TLDR: more testing is needed at this point to determine what's going on with the m1 mac and podman.

[cin]

e2e-tests failure on m1 mac w/podman built images:

+ kind load docker-image -n e2e-tests ibmcom/varnish-operator:local
using podman due to KIND_EXPERIMENTAL_PROVIDER
enabling experimental podman provider
Image: "ibmcom/varnish-operator:local" with ID "01310181d02334a075005a93719350b78e3b80bbf9557b4ef386423a6f0f3cff" not yet present on node "e2e-tests-control-plane", loading...
+ kind load docker-image -n e2e-tests ibmcom/varnish:local
using podman due to KIND_EXPERIMENTAL_PROVIDER
enabling experimental podman provider
Image: "ibmcom/varnish:local" with ID "09c78f243e69900cccf78c18e11eccccf987df349a08ee06eb0c3915f222225d" not yet present on node "e2e-tests-control-plane", loading...
ERROR: failed to load image: command "podman exec --privileged -i e2e-tests-control-plane ctr --namespace=k8s.io images import --digests --snapshotter=overlayfs -" failed with error: exit status 1
Command Output: ctr: image might be filtered out
make: *** [e2e-tests] Error 1