MR analytics - Fix data table column widths

Problem

The column widths for the new MR analytics dashboard make the data table hard to use. The MR title is given too much space and causing the subsequent columns to overflow the dashboard panel, resulting in a horizontal scrollbar.

The problem is even worse on small screens, where only the MR title column is visible.

Solution

We should switch from using a responsive table to a fixed width table. Then we will be able to specify set widths for the table columns. In order to do so, we'll need to add the ability to customize the DataTable visualization via YAML, as the current responsive behaviour is hardcoded

We should also switch to a stacked table for small screen sizes.