Finish extraction

- Moves SwiftUI code out of Riot and into RiotSwiftUI which has no dependency on Matrix SDK.
- Git wasn't smart enough to see the file moves. Most feature function has remain unchanged. 1 change I did make was remove NotificationSettingsViewModel's dependence on MxPushRule, so that the view model could be moved into RiotSwiftUI.
- Add LocaleProvider to abstract VectorL10n's use of Matrix SDK language so it can be used in RiotSwiftUI.
- Split Theme into UKit/SwiftUI version to remove RiotSwiftUI's dependence on ThemeService and ThemeV1.
- Migrated from ThemeObserver to ThemePublisher. We push updates to ThemePublisher so that we can remove ThemeService as dependency.
- Add .DS_Store to .gitignore

RiotSwiftUI/Modules/Room/NotificationSettings/View/VectorForm.swift

@@ -0,0 +1,64 @@
+// 
+// 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
+
+@available(iOS 14.0, *)
+struct VectorForm<Content: View>: View {
+    
+    @Environment(\.theme) var theme: ThemeSwiftUI
+    var content: () -> Content
+    
+    init(@ViewBuilder content: @escaping () -> Content) {
+        self.content = content
+    }
+    
+    var body: some View {
+        ScrollView {
+            VStack(alignment: .leading, spacing: 0, content: content)
+        }
+        .frame(
+            minWidth: 0,
+            maxWidth: .infinity,
+            minHeight: 0,
+            maxHeight: .infinity,
+            alignment: .top
+        )
+        .background(theme.colors.system)
+        .edgesIgnoringSafeArea(.bottom)
+        
+    }
+}
+
+@available(iOS 14.0, *)
+struct VectorForm_Previews: PreviewProvider {
+    
+    static var previews: some View {
+        Group {
+            VectorForm {
+                SwiftUI.Section(header: FormSectionHeader(text: "Section Header")) {
+                    FormPickerItem(title: "Item 1", selected: true)
+                    FormPickerItem(title: "Item 2", selected: false)
+                    FormPickerItem(title: "Item 3", selected: false)
+                }
+            }
+            VectorForm {
+                FormPickerItem(title: "Item 1", selected: true)
+            }
+            .theme(ThemeIdentifier.dark)
+        }
+    }
+}