Direct avatar rendering (#13649)

* Direct avatar rendering

This adds new template helpers for avatar rendering which output image
elements with direct links to avatars which makes them cacheable by the
browsers.

This should be a major performance improvment for pages with many avatars.

* fix avatars of other user's profile pages

* fix top border on user avatar name

* uncircle avatars

* remove old incomplete avatar selector

* use title attribute for name and add it back on blame

* minor refactor

* tweak comments

* fix url path join and adjust test to new result

* dedupe functions

templates/repo/settings/lfs_locks.tmpl

@@ -35,7 +35,7 @@
 							</td>
 							<td>
 								<a href="{{AppSubUrl}}/{{$lock.Owner.Name}}">
-									<img class="ui avatar image" src="{{$lock.Owner.RelAvatarLink}}">
+									{{avatar $lock.Owner}}
 									{{$lock.Owner.DisplayName}}
 								</a>
 							</td>