Display GPG verification state of latest commit in repository and blob view

Description

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9546 introduced displaying the GPG verification state on the commits page. It would be consistent to also display it for the latest commit on the repository page and when navigating to an individual file (blob view).

Proposal

Add the GPG status badge to commit header:

Design

Verified	Unverified

• There is no change in the UI of the popover that appears on clicking the badge.
• The gap between the GPG badge, pipeline status, and the commit ID should be 16px. These three elements should be vertically centered inside the box.
• The pipeline status icon should be 24px in width and height.
• The copy to clipboard button should use duplicate.svg icon from gitlab-svgs. Its currently using an outdated icon.