Keep orphan data by default

Apparently fake users and orphan data is causing a lot of confusion, and there's pressure to overhaul the system.

I would like to suggest a much smaller and easier stop-gap solution, which is to simply keep all orphaned data in the file unless the user explicitly deletes it.

The downsides to this approach can be completely mitigates if when the user closes Blender, together with the "save changes before closing" prompt, they're also presented with how many orphaned pieces of data they have, and how much disk space it is taking up. There's a purge button right there, and they can choose to click it or not.