Timeline item sender profiles (#463)

* Adopt timeline item sender profiles for displaying user avatars and display names
* Prevent images from automatically being evicted from the in-memory cache when entering background
* Get rid of all the `urlString: String`s and start using proper URLs
* Add back manual display name loading as the sender profiles aren't working properly yet
* Implement a sender profile.
* Bump the RustSDK to v1.0.32-alpha

Co-authored-by: Doug <douglase@element.io>

ElementX/Sources/Services/Timeline/TimelineItemProxy.swift

@@ -95,8 +95,11 @@ struct EventTimelineItemProxy: CustomDebugStringConvertible {
         item.isEditable()
     }
     
-    var sender: String {
-        item.sender()
+    var sender: TimelineItemSender {
+        let profile = item.senderProfile()
+        return .init(id: item.sender(),
+                     displayName: profile.displayName,
+                     avatarURL: profile.avatarUrl.flatMap(URL.init(string:)))
     }
 
     var reactions: [Reaction] {