Add signature badge on 'changes' tab of merge request

Proposal

In !67582 (merged), the signature badge for commits is added on the 'Commits' tab. In the course of the review, @pedroms suggested to do this on the 'Changes' tab as well.

🤔 suggestion: to make this consistent when a commit is being viewed in the MR changes tab, can you please also add the verification badge to it?:

See how this looks like in the repository homepage (e.g. ) vs how it looks when you click on a commit in an MR:

Repository	Commit in MR

On smaller viewports, the badge can still be visible here (like we do in the commits list):

Source: !67582 (comment 649571729)