Rename `nvidia.com/accelerator-memory` extended resource

[tardieu]

We should not be using nvidia.com/ as a prefix for a resource name we introduce.

[tardieu]

We should be careful to namespace the two kinds of resources we have at this time. For instance, we could rename:

• nvidia.com/accelerator-memory to org.instaslice.quota/accelerator-memory
• org.instaslice/<uid> to org.instaslice.marker/<uid>

[tardieu]

Since the amount of accelerator-memory available on the node is derived from the GPU inventory on the node and is not guaranteed to reflect the available GPU memory, we should probably include a term like quota in the name of the extended resource to reflect the intent.

[mamy-CS]

/assign @mamy-CS