Submit upstream design enhancements for multi-tenancy

There is an existing PR which is a design proposal to support multi-tenancy: https://github.com/vmware-tanzu/velero/pull/4393
We need to help push this forward. Ideally we should target Velero 1.10 for implementation of this.

We need to sync up with Dave to find out if he is still working this or not. If he is, we should help review with feedback from our prototype. If not, we should suggest allowing us to continue his efforts here.