Add user preference to turn off automatically adding a new list item

Problem

We recently implemented a new feature that automatically adds list items when Enter is hit.

Some users prefer to have exact control over the editing.

Proposal

We should add a user setting, in Preferences > Behavior

This should be implemented in the same fashion as Add user preference to turn off keystroke forma... (#247918 - closed) and Add user preference to turn off keystroke forma... (!53079 - merged)