Switch events and databases class to Keruald packages implementations

Summary:
This is a straightforward move as:

• keruald/database was written from the Obsidian version
• keruald/omnitools got the Events class as is

This is a follow-up of rKERUALD85207350c60e.

Ref T1709

Maniphest Tasks: T1709

Differential Revision: https://devcentral.nasqueron.org/D3774