Automatic merge from submit-queue (batch tested with PRs 40703, 40093, 40618, 40659, 39810)

Change kubemark Makefile to be provider independent

Ref issue #38967

The Kubemark Makefile is defaulted to gcr.io. Instead, make it
provider independent.

The kubemark makefile is set to push the kubemark image to the gcr.io registry. In order to make kubemark not as provider specific, allow the developer to choose a registry.