Add option to disable/enable 'Draggable rows' in configuration form

Problem/Motivation

The feature to drag rows in the entityreference_view widget might be why a page with many rows takes a long time to load.

Steps to reproduce

Open a form where the widget is used and add a lot of rows to it at the same time.

Proposed resolution

Add an option to disable/enable draggable rows in the widget.

Remaining tasks

User interface changes

API changes

Data model changes