Simplify handling of renovate PRs by configuring a merge queue

[DiamondJoseph]

As our PRs require that the branch is up to date with the default branch, it can be frustrating to merge multiple dependency updates from renovate: you approve multiple PRs, going to merge the first and the others must merge main into themselves before they can continue.

Configuring a merge queue would allow us to queue up these PRs to sequentially merge one after the other.

https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-a-merge-queue

I believe when we have used this before (was the default behaviour of the repo maybe?) we had not configured the workflow to run on merge_group?

Acceptance Criteria

• Specific criteria that will be used to judge if the issue is fixed