RD-14980: CRUD support

[bgaidioz]

• Unique column is picked from Databricks table metadata,
  • only the case of a single column primary key is supported,
  • if not found, we return the first column, but that's only to satisfy the das-protocol. We later fail UPDATE/DELETE.
• Some fixes/refactoring of the execution of a query to ensure errors are handled by the caller,
• INSERT can be done in batches but by forging a large query with inlined data, some logic there to split the calls into reasonable sized query strings.