Add new label for .mailmap and verified commits

What does this MR do and why?

Adds a new label for commits which are verified but have a commit author email which is not verified to the committer.

Gitaly supports [git mailmap](https://git-scm.com/docs/gitmailmap) behind a feature flag. Mailmap allows repositories to include a file which will map commit email addresses to new addresses. When a email address has been mapped to an unverified email address, this MR will relabel verified commits as shown below.

To do this we check the commit email against the signature email for verified commits.

There are 5 ways in which we can sign commits.

UI signing with SSH and GPG, user signing with SSH, GPG and X509.

We need to handle all cases.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

Follow the description in https://gitlab.com/gitlab-org/gitlab/-/issues/425042 to setup a mailmap user mapping.

See verified commits which were previously labels as verified now labelled as ⚠ Verified with an orange label.

Hovering over the label:

Related to #425042