Revert weak media provider (#4483)

* Revert "Address the real lifetime issue of the SDK's `Client` by making `Context.mediaProvider` weak. (#4466)"

This reverts commit c794144ef1.

* Better docs.

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -73,7 +73,7 @@ enum TimelineMediaVisibility: Decodable {
 }
 
 // sourcery: AutoMockable
-protocol ClientProxyProtocol: AnyObject, MediaLoaderProtocol {
+protocol ClientProxyProtocol: AnyObject {
     var actionsPublisher: AnyPublisher<ClientProxyAction, Never> { get }
     
     var loadingStatePublisher: CurrentValuePublisher<ClientProxyLoadingState, Never> { get }
@@ -105,6 +105,8 @@ protocol ClientProxyProtocol: AnyObject, MediaLoaderProtocol {
     
     var pusherNotificationClientIdentifier: String? { get }
     
+    var mediaLoader: MediaLoaderProtocol { get }
+    
     var roomSummaryProvider: RoomSummaryProviderProtocol { get }
     
     /// Used for listing rooms that shouldn't be affected by the main `roomSummaryProvider` filtering