Add an icon to show if a merge request is set to auto-merge

Proposal

When a merge request is set to auto-merge when checks pass, we should display that in the merge request list.

• Does adding to merge train require a different indicator?

A new icon is required as there is nothing at the moment that would represent "auto-merge".

From #533850 (comment 2491258914)

include an icon for MRs that MWPS