Megha/cd pipeline enhancement

[meghalims]

This PR introduces improvements to the Dgraph CD pipeline so that ARM and AMD images are saved as artifacts (dgraph-docker-amd64 and dgraph-docker-arm64) in the respective build jobs and utilizes these in the manifest creation job later.

Key Changes:

• Save Docker Image Artifacts for Dgraph and Standalone Images - in both AMD and ARM Jobs
• The dgraph-docker-image-and-manifest job downloads the saved artifacts and loads them back into Docker using docker load, ensuring consistency across the workflow.