Migration to GHA

[alexandreLamarre]

• Adds goreleaser for binary release CI, a standard release tool for go binaries. Preserves the same static link flags as our package script
• Migrates main CI (build & test) to gha dynamic matrices (linuxamd, linuxarm) x (min_supported_k8s-version, max_supported_k8s_version)
• Migrates image building CI to using docker-build-and-push action using buildx and docker manifests.

⚠️ Does not include arm64 support, will follow up in a separate PR on this

• example goreleaser CI
• example publish CI

[ericpromislow]

Just nits. The CI files look good, and it's helpful that the github actions are passing.

[mallardduck]

LGTM.

@ericpromislow - IIRC you said you would handle this round of release stuff for BRO. So if we merge this before that release then this will most directly affect you, so i'll mostly defer to your call - beyond this initial review.

[ericpromislow]

Looks good now