[WIP] Implement abstractions to annotate non-sharable datasets & objectstores.

[jmchilton]

Sketched out so far:

• Allow marking objectstores (in either XML or YAML) as private - indicating datasets stored in them should not be shared.
• Add sharable property to model.Dataset that checks its object_store_id against the configured object store to determine if it is not stored in a private objectstore.
• Add abstraction to security_agent to check if a dataset is restricted to a single user and augment galaxy.jobs.JobWrapper._set_object_store_ids and ObjectStorePopulator to prevent jobs that might create non-private datasets in private objectstores.
• Model/security layer prevents copying non-sharable dataset into libraries or attaching private sharing roles to them.
• The edit metadata form will display a message that the dataset is unsharable on the permissions page.
• Integration test case to ensure cannot upload public datasets to a private objectstore.
• Integration test case to ensure cannot modify access permissions of datasets stored in private objectstores.
• Expose information about whether objectstores are private in newly merged ObjectStore metadata display (User-facing objectstore metadata. #10233).

Left to do:

• Test case to verify library sets can't be uploaded to private objectstores.
• Test case to verify private object stores operate appropriately with dynamically discovered collection datasets. (past @jmchilton had this in his notes - not sure exactly what his concern was).

xrefs:

• The Nate white paper on related things (https://docs.google.com/document/d/1TQCbQxwLLijKHl_sZgTDQCpNXX2jejJQBljVrNslOvA/edit)
• Implementing quotas per objectstore Implement quota tracking options per ObjectStore. #10221
• Per-user objectstore configurations User-based ObjectStore #4840

[jmchilton]

Rebased this on 21.09... a rebase of that on to 22.01 is in branch sharable_data_2201.