Document or remove WorkspaceName from porch PackageRevision spec

[ciaranjohnston]

WorkspaceName is a parameter that forms part of the PackageRevision spec:
https://github.com/nephio-project/porch/blob/cb1b392069de7711bb29c3524d6fc464e991f82a/api/porch/v1alpha1/types.go#L71

It is used to handle multiple packagerevision drafts coexisting in parallel. It may well be cleaner to handle this using multiple PackageRevision instances in a draft stage as visualized in slide 6 here:
https://docs.google.com/presentation/d/1RVed0AViyPlhg4XZckrmpeUI1ClYM8or/edit#slide=id.g30ae98f1e62_2_14

The use of workspacename should be documented in the Porch API / user documentation or an alternative approach to handing multiple drafts in parallel be implemented.

This issue is a result of a discussion around this user story proposal:
https://docs.google.com/document/d/1d4USe4nOcOQAb0ULCMGSPtC72f0dbV0SguPCPEGYaac/edit?tab=t.0

[ciaranjohnston]

Needs investigation to determine the optimal way to handle drafts, to avoid merge conflict complexity.