Unify getUser

Always use `NeoChatRoom::getUser` for getting user details in a room context.
- `MessageEventModel` now calls `getUser`
- `getUser` is now overloaded to also be able to take a `NeoChatUser*`
- add params to `getUser` that are needed for the model outputs

src/qml/Component/Timeline/LocationDelegate.qml

@@ -93,7 +93,7 @@ TimelineContainer {
                         visible: root.asset === "m.self"
                         width: height
                         height: parent.height / 3 + 1
-                        name: root.author.name ?? root.author.displayName
+                        name: root.author.displayName
                         source: root.author.avatarSource
                         color: root.author.color
                     }