Adopt sliding sync versions for client Restoration.

ElementX/Sources/Services/Client/ClientProxy.swift

@@ -210,6 +210,16 @@ class ClientProxy: ClientProxyProtocol {
         client.homeserver()
     }
     
+    var slidingSyncVersion: SlidingSyncVersion {
+        client.slidingSyncVersion()
+    }
+    
+    var availableSlidingSyncVersions: [SlidingSyncVersion] {
+        get async {
+            await client.availableSlidingSyncVersions()
+        }
+    }
+    
     var userIDServerName: String? {
         do {
             return try client.userIdServerName()

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -104,8 +104,11 @@ protocol ClientProxyProtocol: AnyObject, MediaLoaderProtocol {
 
     var homeserver: String { get }
     
+    var slidingSyncVersion: SlidingSyncVersion { get }
+    var availableSlidingSyncVersions: [SlidingSyncVersion] { get async }
+    
     var userIDServerName: String? { get }
-        
+    
     var userDisplayNamePublisher: CurrentValuePublisher<String?, Never> { get }
 
     var userAvatarURLPublisher: CurrentValuePublisher<URL?, Never> { get }