[ANCHOR-1190] Fix multi-arch image build

[JiahuiWho]

Description

• Switch to Docker's recommended pattern:
  • Build jobs push by digest only (no intermediate -amd64 -arm64 tags)
  • Then a create_multi_arch_manifest job uses docker buildx imagetools create to merge both digests into a single multi-arch manifest.
• Apply the same fix to on_push_to_develop

Context

#1922 failed because docker manifest create (used to merge the amd64 and arm64 builds) expects each source image to be a plain image manifest. However, build-push-action v6 with buildx wraps each single-platform image into a manifest list (containing the image + provenance attestation), so the command rejects them with the error "is a manifest list"

Testing

• ./gradlew test

Documentation

N/A

Known limitations

N/A

[Copilot]

Pull request overview

Updates the Docker publishing workflows to follow Docker’s recommended multi-arch pattern: push per-arch images by digest, then merge those digests into a single multi-arch manifest using docker buildx imagetools create. This addresses failures caused by trying to merge per-platform manifest lists with docker manifest create.

Changes:

• Build amd64/arm64 images and push them by digest (no intermediate arch tags).
• Create and push multi-arch manifests (release version/latest; develop edge/dated) via docker buildx imagetools create using the per-job digests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/on_release_created_or_updated.yml	Push per-arch images by digest and create release multi-arch manifests from digests.
.github/workflows/on_push_to_develop.yml	Apply the same digest + imagetools create pattern for edge and dated edge-* tags.

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