UITests and Mock Screens

Adds the test targets for Unit and UI tests
Adds mock screen data and utilities to render each mock screen for previews/ui tests.
Changes Published property in the service to CurrentValueSubject. we don't need the synthesized aspect of Published and property wrappers cannot be included in protocols.

RiotSwiftUI/Modules/Common/Mock/MockScreen.swift

@@ -0,0 +1,58 @@
+// 
+// Copyright 2021 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 SwiftUI
+
+/*
+ Used for mocking top level screens and their various state.
+ */
+@available(iOS 14.0, *)
+protocol MockScreen {
+    associatedtype ScreenType: View
+    static func screen(for state: Self) -> ScreenType
+    static var screenStates: [Self] { get }
+}
+
+
+@available(iOS 14.0, *)
+extension MockScreen {
+    
+    /*
+     Get a list of the screens for every screen state.
+     */
+    static var screens: [ScreenType] {
+        Self.screenStates.map(screen(for:))
+    }
+    
+    /*
+     Render each of the screen states in a group applying
+     any optional environment variables.
+     */
+    static func screenGroup(
+        themeId: ThemeIdentifier = .light,
+        locale: Locale = Locale.current,
+        sizeCategory: ContentSizeCategory = ContentSizeCategory.medium
+    ) -> some View {
+        Group {
+            ForEach(0..<screens.count) { index in
+                screens[index]
+            }
+        }
+        .theme(themeId)
+        .environment(\.locale, locale)
+        .environment(\.sizeCategory, sizeCategory)
+    }
+}