Adding support for linux/ppc64le in CI for centraldashboard multi-arc…

[amitmukati-2604]

…h docker images

[amitmukati-2604]

• The workflow "centraldb_docker_publish" releases docker image for Linux-amd64.
• Added docker-build-multi-arch and build-push-multi-arch targets in the Makefile of the Tensorboard-controller component.
• Dropping docker-build and docker-push from the workflow.
• Keeping these steps will increase the workflow runtime.
• Docker-build-push-multi-arch builds and pushes the images for Linux-amd64 and Linux-ppc64le

[kimwnasptd]

@apo-ger could you also take a stab at it? Should be the same with the rest of the updates we did for ppc64le

/cc @apo-ger

[apo-ger]

Changes look good!
/lgtm

[apo-ger]

/remove-lgtm

Actually I'm getting an error while trying to build the image.

EDIT: Apologies for the confusion, everything work as expected!

[apo-ger]

/lgtm

[lehrig]

/assign @StefanoFioravanzo

...just needs an approval now.

[kimwnasptd]

/approve

[google-oss-prow]

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