Factorize the duplicated user-with-avatar display macro in likers.vm and getusers.vm

`likers.vm` and `getusers.vm` each define their own local, identical `#displayUserAliasWithAvatar($userReference $disabled)` Velocity macro to render a user's avatar + link, instead of reusing the standard `displayUser` macro from `macros.vm`.

This is a maintenance problem: the two templates carry duplicated markup/logic for something XWiki already has a shared, standard macro for. Any future change to how a user is displayed (permission handling, styling, accessibility, etc. — e.g. the non-viewable-user handling fixed in XWIKI-23995) has to be found and re-applied in both copies instead of being fixed once in `displayUser`. The local macros also lag behind `displayUser` in capability, since they were never touched when that macro evolved.

This ticket is about eliminating that duplication so both templates go through the standard `displayUser` macro, with no visible change in how users are rendered in either template.