[FEATURE] Improve permission granularity for tenants

[uj-ff48]

Is your feature request related to a problem?
Read only users of a tenant cannot save searches. This makes impossible for such an user to create/download a report, even if it got the rights.
What solution would you like?
It would be desirable to improve the permission granularity when it comes to tenant rights.
For instance, I would like to specify what kind of tenant object is writeable: kibana:saved_objects/search/write.
What alternatives have you considered?
A simple solution is to force r/o users to work on their private tenant, but people are lazy and do not want to import objects into their own space (and take responsibility).

[stephen-crawford]

[Triage] Hi @uj-ff48, thank you for filing this issue. @davidlago could you follow-up on this? Thank you.

[davidlago]

Thanks for the tag, @scrawfor99. Closing this one and linking to the new workspaces effort that is the reincarnation of tenants, where the way these are access controlled will be improved opensearch-project/OpenSearch-Dashboards#4615.