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

Tools/SwiftGen/Templates/Strings/flat-swift4-vector.stencil

@@ -66,12 +66,10 @@ extension {{enumName}} {
     let format = NSLocalizedString(key, tableName: table, bundle: Bundle(for: BundleToken.self), comment: "")
     let locale: Locale
         
-    if let localeIdentifier = Bundle.mxk_language() {
-       locale = Locale(identifier: localeIdentifier)
-    } else if let fallbackLocaleIdentifier = Bundle.mxk_fallbackLanguage() {
-       locale = Locale(identifier: fallbackLocaleIdentifier)
+    if let providedLocale = LocaleProvider.locale {
+      locale = providedLocale
     } else {
-       locale = Locale.current
+      locale = Locale.current
     }        
 
       return String(format: format, locale: locale, arguments: args)
@@ -81,4 +79,4 @@ extension {{enumName}} {
 private final class BundleToken {}
 {% else %}
 // No string found
-{% endif %}
+{% endif %}