Private Datasets: Implement ReBAC-related data persistent storage + `DatasetEntryRepository` (database variants)

[s373r]

This ticket is a continuation of this one, to add database repository variants.

In other words, needs to be introduced:

• DatasetEntryRepository implementations for databases (SQLite, PostgreSQL).
• RebacRepository implementations for databases (=/=).

Steps

• [x] SQLite https://github.com/kamu-data/kamu-cli/pull/771
• [x] PostgreSQL https://github.com/kamu-data/kamu-cli/pull/869

[s373r]

All sub-tickets have been completed