Prototype the RBAC Python API with vfolder-related operations

[achimnol]

Let's explore the design of RBAC Python API with the following user scenarios.
At this stage, we won't implement the actual RBAC subsystem but only apply the interface invocations.

Phase 1-1

• query_accessible_vfolders()
• vfolder_host_permissions
• vfolder_permission_required

PRs:

• materialize storage host rbac apis #2264
• refactor: impl vfolder RBAC APIs #2137
• refactor: apply new vfolder RBAC APIs to api modules #2138
• fix: Filter out host permissions of model store #2117

Phase 1-2

• "mode store" project
• project administrator

Related issues

• Implement vfolder-host access control #753
• Rename query_accessible_vfolders to query_mountable_vfolders #1387
• Represent shared/invited vfolders as rows of the vfolders table #1955
• Upload-only mode for vfolders #1992