[CI] Pull Ubuntu base image from internal registry

This MR updates the Docker build process for OAI images to use a private registry for the Ubuntu base image ubuntu:noble. This will reduce the possibility for CI disruption if no internet connection exists.

• Replace FROM ubuntu:noble with FROM <DEFAULT_REGISTRY>/ubuntu:noble in Ubuntu Dockerfiles.

This change overcomes the pull rate limit issues from DockerHub in the CI.

The <DEFAULT_REGISTRY> contains a multi-architecture image (arm64 and amd64)

$ docker buildx imagetools inspect gracehopper3-oai.sboai.cs.eurecom.fr/ubuntu:noble | grep Platform
  Platform:  linux/amd64
  Platform:  linux/arm64

• The scripts run from the jenkins server everyday using a crontab.
• It pulls the AMD and ARM ubuntu:noble image on respective servers and checks if the internal registry is in sync.
• If not, it pushes the ubuntu:noble image to the registry to remain in sync with dockerhub.