Add aconfig flag: notification_async_group_header_inflation

Add aconfig flag: notification_async_group_header_inflation to control the async notification group summary inflation.

Bug: 217799515
Test: atest SystemUITests
Flag: ACONFIG notification_async_group_header_inflation DEVELOPMENT
Change-Id: Ibd5fb22fcf202457ee79625104ea1d2fef8b91a3
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index c23a49c..98d3f9e 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -15,6 +15,13 @@
 }
 
 flag {
+    name: "notification_async_group_header_inflation"
+    namespace: "systemui"
+    description: "Inflates the notification group summary header views from the background thread."
+    bug: "217799515"
+}
+
+flag {
     name: "notification_async_hybrid_view_inflation"
     namespace: "systemui"
     description: "Inflates hybrid (single-line) notification views from the background thread."