Rework modifications callback

We are firing the modification callbacks manually, which sucks when the change comes from a distant path (for instance, a folder gets removed, which triggers multiple media deletion)

Instead, let's leverage the sqlite hooks to fire the callbacks.

• Pass entities IDs instead of the entities themselves to the modification callback (std::vector<FooPtr> -> std::vector<int64_t>)
• Remove manual events firing
• Plug modification callbacks to the sqlite hooks