Split files

[ivnsch]

While large files are not necessarily bad, if the components inside are decoupled, we have some issues in reports_updater.rs:

• We can't see easily which tests belong to what.
• Autoformat stopped working (at for me) in this file.
• Database currently is in preferences.rs, which is misplaced. This should be also in a separate file.
• Move anything else that seems misplaced to its own / another file.