Added unit tests for NotificationManager (#376)

* NotificationManager tests

* More unit tests

* More tests, moved classes to separate files

* Removed warnings

* UserNotificationCenterProtocol as AnyObject

* Reverted back Package.resolved

ElementX/Sources/Services/Notification/Manager/UserNotificationCenterProtocol.swift

@@ -0,0 +1,25 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import UserNotifications
+
+protocol UserNotificationCenterProtocol: AnyObject {
+    var delegate: UNUserNotificationCenterDelegate? { get set }
+    func add(_ request: UNNotificationRequest, withCompletionHandler completionHandler: ((Error?) -> Void)?)
+    func requestAuthorization(options: UNAuthorizationOptions, completionHandler: @escaping (Bool, Error?) -> Void)
+    func setNotificationCategories(_ categories: Set<UNNotificationCategory>)
+}