Better Feedback for Unverified commit signatures

Proposal

Currently the modal for displaying the verification of a git signature shows very little information

If you want to know "why" your signature is reading as "unverified" there is little to know UI feedback to highlight which criteria it doesn't mean. Email missing, no trusted root CA, or unsupported signing type would all be useful feedback to provide to help a user sign their commits correctly, but currently there is no real way to determine which criteria the commit signature fails to meet.

We should therefore expand the modal to provide feedback on one or more verification checks that signatures failed to meet whenever they are unverified. This should be usable for GPG, X509 and SSH signatures.

Implementation proposal (by @vyaklushin)

Extend the list of [verification statuses](For X.509 we define only two statuses for X.509 signatures. An example - SSH keys signature statuses.