ARM64 / Multi-Arch Docker Support

Feature request description

Build ARM64-compatible container images and release them with manifest lists so multiple architectures can take advantage of the same tags from the image repo.

Is your feature request related to a problem? If so, please describe.

I would like to experiment with Sourcegraph with some of my/my company's private repositories, but the most convenient place for me to run my a self-hosted Sourcegraph server would be on a Raspberry Pi 4, which has a Cortex-A72 ARM CPU. The majority of Sourcegraphs images used by services in the deploy-sourcegraph-docker repository and the all-in-one 'quick start' self-hosted page are x86/64 only.

With the rise of ARM instruction sets in the office, at home and on servers, it would be advantageous to support at least that architecture.

(Note I'm not saying that running a service as demanding as Sourcegraph on an rpi is necessarily a good idea, it's just what I happened to have at hand)

Describe alternatives you've considered.

I could provision an x86/64 instance to run it elsewhere, but this is inconvenient when I have unused compute locally
I could run it on my development laptop, which happens to be x86/64, but this would result in reduced performance and it isn't an option for everyone, eg. my colleagues have ARM64 Macs as their daily drivers
I did have a quick look to see if I would be able to adapt your build process to support ARM64, but I'm not familiar with Bazel and I'm not sure where to start to even find the all-in-one container image build source

For the moment, I've decided not to run a private Sourcegraph, at least until I have an AMD64 server with spare resources.

Additional context

I did look for previous issues that had been opened related to this request, but wasn't able to find any. Apologies if this is a duplicate.

sourcegraph / sourcegraph-public-snapshot