Our main maintainers can use testground on their local machine

[laurentsenta]

Piotr & Marteen can't use testground right now because of M1 compatibility.
From what we've seen in the code, the GOARCH=amd64 is "just" a copy and past from another project.

• fix the build for arm
• Ideally, we'd start distribute Docker images and testground binaries that could be reused

[laurentsenta]

Notes:
https://docs.docker.com/desktop/multi-arch/#build-multi-arch-images-with-buildx

(raised a question in the main repo)

• opened the discussion of renting M1 in discord.

[laurentsenta]

(not a prio, they can use a remote testground setup for now)