Speedup the release process

[maksym-iv-ef]

Mermin release flow may be relatively slow due to multi-arch builds on a single arch.

The build process should be improved to use multiple multi-arch GH runners.

Note, it's important to push by digest (--output push-by-digest=true,type=image,push=true ) and combining to a single manifest via

docker buildx imagetools create \
  -t IMAGE:TAG \
  IMAGE@sha256:SHA \
  IMAGE@sha256:SHA

Otherwise, the "last" pushed image will override previous ones for a given tag if pushing by tag.