fix(ci) avoid OOM when building with QEMU

We seem to be close to the QEMU memory limit in GHA, that's why actions
fail sporadically.

Switch to native builds, aka build amd64 in an amd64 machine and do the
same for arm64.

This means we need to push 2 extra tags: foo-amd64 and foo-arm64 and
then create a manifest to unite them both.

Ref: docker/build-push-action#621

Author: saghul