chore(ui,core,llc,persistance,localization): change AppBar props

packages/stream_chat_flutter/lib/src/channel_header.dart

@@ -138,14 +138,17 @@ class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
             break;
         }
 
+        final theme = Theme.of(context);
+
         return InfoTile(
           showMessage: showConnectionStateTile && showStatus,
           message: statusString,
           child: AppBar(
-            titleTextStyle: Theme.of(context).appBarTheme.titleTextStyle,
-            systemOverlayStyle: Theme.of(context).brightness == Brightness.dark
-                ? SystemUiOverlayStyle.dark
-                : SystemUiOverlayStyle.light,
+            toolbarTextStyle: theme.textTheme.bodyText2,
+            titleTextStyle: theme.textTheme.headline6,
+            systemOverlayStyle: theme.brightness == Brightness.dark
+                ? SystemUiOverlayStyle.light
+                : SystemUiOverlayStyle.dark,
             elevation: 1,
             leading: leadingWidget,
             backgroundColor: backgroundColor ?? channelHeaderTheme.color,

packages/stream_chat_flutter/lib/src/channel_list_header.dart

@@ -122,14 +122,16 @@ class ChannelListHeader extends StatelessWidget implements PreferredSizeWidget {
 
         final chatThemeData = StreamChatTheme.of(context);
         final channelListHeaderThemeData = ChannelListHeaderTheme.of(context);
+        final theme = Theme.of(context);
         return InfoTile(
           showMessage: showConnectionStateTile && showStatus,
           message: statusString,
           child: AppBar(
-            titleTextStyle: Theme.of(context).appBarTheme.titleTextStyle,
-            systemOverlayStyle: Theme.of(context).brightness == Brightness.dark
-                ? SystemUiOverlayStyle.dark
-                : SystemUiOverlayStyle.light,
+            toolbarTextStyle: theme.textTheme.bodyText2,
+            titleTextStyle: theme.textTheme.headline6,
+            systemOverlayStyle: theme.brightness == Brightness.dark
+                ? SystemUiOverlayStyle.light
+                : SystemUiOverlayStyle.dark,
             elevation: 1,
             backgroundColor:
                 backgroundColor ?? channelListHeaderThemeData.color,

packages/stream_chat_flutter/lib/src/gallery_header.dart

@@ -58,11 +58,13 @@ class GalleryHeader extends StatelessWidget implements PreferredSizeWidget {
   @override
   Widget build(BuildContext context) {
     final galleryHeaderThemeData = GalleryHeaderTheme.of(context);
+    final theme = Theme.of(context);
     return AppBar(
-      titleTextStyle: Theme.of(context).appBarTheme.titleTextStyle,
-      systemOverlayStyle: Theme.of(context).brightness == Brightness.dark
-          ? SystemUiOverlayStyle.dark
-          : SystemUiOverlayStyle.light,
+      toolbarTextStyle: theme.textTheme.bodyText2,
+      titleTextStyle: theme.textTheme.headline6,
+      systemOverlayStyle: theme.brightness == Brightness.dark
+          ? SystemUiOverlayStyle.light
+          : SystemUiOverlayStyle.dark,
       elevation: 1,
       leading: showBackButton
           ? IconButton(

packages/stream_chat_flutter/lib/src/thread_header.dart

@@ -128,12 +128,14 @@ class ThreadHeader extends StatelessWidget implements PreferredSizeWidget {
           ],
         );
 
+    final theme = Theme.of(context);
     return AppBar(
       automaticallyImplyLeading: false,
-      titleTextStyle: Theme.of(context).appBarTheme.titleTextStyle,
-      systemOverlayStyle: Theme.of(context).brightness == Brightness.dark
-          ? SystemUiOverlayStyle.dark
-          : SystemUiOverlayStyle.light,
+      toolbarTextStyle: theme.textTheme.bodyText2,
+      titleTextStyle: theme.textTheme.headline6,
+      systemOverlayStyle: theme.brightness == Brightness.dark
+          ? SystemUiOverlayStyle.light
+          : SystemUiOverlayStyle.dark,
       elevation: 1,
       leading: leading ??
           (showBackButton