feat: Build multiarch images

[jiparis]

This PR introduces changes for building multiarch images with goreleaser. Note that it needs buildx, which in turn uses qemu binaries (that's the reason for the workflow changes).

Basically duplicates all docker configurations for both architectures (I've already checked that we use multiarch base images), and adds new docker_manifests for the multiarch index manifests.

Building locally:

> goreleaser release --clean --snapshot --skip=sign,sbom
...

Running (see the warning for AMD in MacOS with Rosetta)

✗ docker run ghcr.io/chainloop-dev/chainloop/cli:v0.96.2-amd64
WARNING: The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
Chainloop Command Line Interface

Usage:
  chainloop [command]
...

✗ docker run ghcr.io/chainloop-dev/chainloop/cli:v0.96.2-arm64
Chainloop Command Line Interface

Usage:
  chainloop [command]

closes #1256

[javirln]

Can this potentially break the images in the charts? Because of the change in the tag basically

[jiparis]

Note that in the section below we are pushing this tag again, but as multiarch image instead. So basically nothing has changed.

[migmartri]

nevemind, ignore my comments, I just read https://goreleaser.com/cookbooks/multi-platform-docker-images/#other-things-to-pay-attention-to

It would be useful to help reviewers to show any context of that change, i.e that link. The change is not trivial.

Thanks!

[migmartri]

are you sure we are tagging with

"ghcr.io/chainloop-dev/chainloop/control-plane:{{ .Tag }}"?

also, do we need to have a different tag? I thought that it was in the same tag?

[jiparis]

Tagging is done in docker_manifests section. Now {{ .Tag }} and latest are index manifests.