Display an icon in the room header for rooms with shared history (#5016)

* feat: Display an icon in the room header for rooms with shared history

* fix: Apply suggestions from code review

- Simplifies `isRoomHistoryShared` expressions using type inferrence.
- Adds failure messages to unit test.

Co-authored-by: Doug <6060466+pixlwave@users.noreply.github.com>

* fix: Remove extension method in favour of field on configuration.

* fix: Distinguish between `shared` and `worldReadable` icons.

* refactor: Use `RoomHistorySharingState` enum with extension methods

---------

Co-authored-by: Doug <6060466+pixlwave@users.noreply.github.com>

ElementX/Sources/Screens/RoomScreen/RoomScreenModels.swift

@@ -7,6 +7,7 @@
 //
 
 import Foundation
+import MatrixRustSDK
 import OrderedCollections
 
 enum RoomScreenViewModelAction: Equatable {
@@ -80,6 +81,9 @@ struct RoomScreenViewState: BindableState {
             (canAcceptKnocks || canDeclineKnocks || canBan)
     }
     
+    /// If `enableKeyShareOnInvite` is set, determines the current history sharing state.
+    var roomHistorySharingState: RoomHistorySharingState?
+    
     var footerDetails: RoomScreenFooterViewDetails?
     
     var bindings = RoomScreenViewStateBindings()