Show Signer in commit lists and add basic trust (#10425) (#10524)

Backport #10425
Backport #10511

* Show Signer in commit lists and add basic trust (#10425)

Show the avatar of the signer in the commit list pages as we do not
enforce that the signer is an author or committer. This makes it
clearer who has signed the commit.

Also display commits signed by non-members differently from
members and in particular make it clear when a non-member signer
is different from the committer to help reduce the risk of
spoofing.

Signed-off-by: Andrew Thornton <art27@cantab.net>

Fix the signing icon in the  view_list.tmpl page (#10511)

Co-Authored-By: silverwind <me@silverwind.io>
Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

docs/content/doc/features/comparison.en-us.md

@@ -60,7 +60,7 @@ _Symbols used in table:_
 | Git LFS 2.0 | ✓ | ✘ | ✓ | ✓ | ✓ | ⁄ | ✓ |
 | Group Milestones | ✘ | ✘ | ✘ | ✓ | ✓ | ✘ | ✘ |
 | Granular user roles (Code, Issues, Wiki etc) | ✓ | ✘ | ✘ | ✓ | ✓ | ✘ | ✘ |
-| Verified Committer | ✘ | ✘ | ? | ✓ | ✓ | ✓ | ✘ |
+| Verified Committer | ⁄ | ✘ | ? | ✓ | ✓ | ✓ | ✘ |
 | GPG Signed Commits | ✓ | ✘ | ✓ | ✓ | ✓ | ✓ | ✓ |
 | Reject unsigned commits | [✘](https://github.com/go-gitea/gitea/issues/2770) | ✘ | ✓ | ✓ | ✓ | ✘ | ✓ |
 | Repository Activity page | ✓ | ✘ | ✓ | ✓ | ✓ | ✓ | ✓ |