Notification Handler to handle notifications in foreground (#837)

* changed how the notifications are handled

* local notifications can be decrypted and shown!

* Improved the handling for the mock and for the normal messages

* Avatar images are also displayed

* pr ready, commented some code that is not supposed to be releaaed yet, adjusted some tests and added some source code in the targets

* fixing some swiftlint complaints and removed an unused function

* better swiftlint disable

* addressing PR comments

UnitTests/Sources/MediaProvider/MediaLoaderTests.swift

@@ -55,8 +55,6 @@ final class MediaLoaderTests: XCTestCase {
 }
 
 private class MockMediaLoadingClient: ClientProtocol {
-    func setNotificationDelegate(notificationDelegate: MatrixRustSDK.NotificationDelegate?) { }
-
     private(set) var numberOfInvocations = 0
     
     func getMediaContent(mediaSource: MatrixRustSDK.MediaSource) throws -> [UInt8] {
@@ -146,4 +144,6 @@ private class MockMediaLoadingClient: ClientProtocol {
     }
     
     func searchUsers(searchTerm: String, limit: UInt64) throws -> MatrixRustSDK.SearchUsersResults { fatalError() }
+
+    func setNotificationDelegate(notificationDelegate: MatrixRustSDK.NotificationDelegate?) { }
 }