Setting to allow empty notes to be deleted rather than just showing `New note...`

### What
A setting that allows empty notes to be automatically deleted rather than just showing `New note...`.

This is the default behaviour of Apple Notes.

### Why
If I go through a bunch of notes and delete the contents (lets say cutting to another notes app/file, or because I'm ticking off todos) then I end up with lots of empty notes at the top of my notes list just saying `New note...` that I then have to go through and delete manually.

No files or tests are named. Start by locating the note deletion flow and the settings entry points, then trace what happens when a note becomes empty. Done means an optional setting causes emptied notes to be deleted while preserving the current behavior when it is disabled.

Written by the indexing model from the issue text.