Cached avatar support (from Rust) (#633)

* loading a cached avatar at first, and then actually doing the request so that the avatar can still be displayed without connection

* improved the code

* fix + changelog

* policy on how to fetch the avatar url added

* code improvements

* addressed al PR comments

* improved the error handling

* improved the async task code

* fixed a typo

* fixed another typo

ElementX/Sources/Screens/Settings/SettingsScreenViewModel.swift

@@ -43,11 +43,13 @@ class SettingsScreenViewModel: SettingsScreenViewModelType, SettingsScreenViewMo
         ServiceLocator.shared.settings.$timelineStyle
             .weakAssign(to: \.state.bindings.timelineStyle, on: self)
             .store(in: &cancellables)
+
+        userSession.clientProxy.avatarURLPublisher
+            .weakAssign(to: \.state.userAvatarURL, on: self)
+            .store(in: &cancellables)
         
         Task {
-            if case let .success(userAvatarURL) = await userSession.clientProxy.loadUserAvatarURL() {
-                state.userAvatarURL = userAvatarURL
-            }
+            await userSession.clientProxy.loadUserAvatarURL()
         }
         
         Task {