Cleanup how we setup the CallKit provider and have it be used for outgoing calls as well (#2967)

- tear down ElementCall screens when ending the call from the CXCallController
- make the call UI available in the task manager and lock screen
- Fix broken hang up widget message format

ElementX/Sources/Mocks/ElementCallServiceMock.swift

@@ -0,0 +1,28 @@
+//
+// Copyright 2024 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 Combine
+import Foundation
+
+struct ElementCallServiceMockConfiguration { }
+
+extension ElementCallServiceMock {
+    convenience init(_ configuration: ElementCallServiceMockConfiguration) {
+        self.init()
+        
+        underlyingActions = PassthroughSubject().eraseToAnyPublisher()
+    }
+}