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 https://gitlab.com/gitlab-org/gitlab/-/issues/533850#note_2491258914
> include an icon for MRs that MWPS
issue