Introduce cloud storage based aliases

It would be great if TensorBoard allowed the usage of aliases to reference to experiments by a stable ID of one's choosing. One possibility to control the attribution of this "alias namespace" would be to base it on existing cloud storage namespaces, e.g. tensorboard dev upload --logdir=gs://flax_data/examples/imagenet would automatically reference to the alias gs/flax_data/examples/imagenet and could then be accessed via https://tensorboard.dev/cloud/gs/flax_data/examples/imagenet

Initially, TensorBoard could support the gs/ alias namespace based on Google Cloud Storage, but this might be extended later on to other cloud storages.