[Drag To Hide] Shows notification when user drag-to-hide a11y floating button

* Click on notification to bring back a11y floating button
* Swipe notification to remove a11y floating button and its services
* A11y service key changed to dismiss notification
* Align to create ACCESSIBILITY channel in systemui NotificationChannels

Bug: 298718415
Flag: ACONFIG com.android.systemui.floating_menu_drag_to_hide DEVELOPMENT
Test: atest MenuViewLayerTest MenuNotificationFactoryTest NotificationChannelsTest

Change-Id: Ie209ec946ea15903acfa6913492605277e9d7057
diff --git a/packages/SystemUI/aconfig/accessibility.aconfig b/packages/SystemUI/aconfig/accessibility.aconfig
index 21263a9..f7b1a26 100644
--- a/packages/SystemUI/aconfig/accessibility.aconfig
+++ b/packages/SystemUI/aconfig/accessibility.aconfig
@@ -10,6 +10,13 @@
 }
 
 flag {
+    name: "floating_menu_drag_to_hide"
+    namespace: "accessibility"
+    description: "Allows users to hide the FAB then use notification to dismiss or bring it back."
+    bug: "298718415"
+}
+
+flag {
     name: "floating_menu_ime_displacement_animation"
     namespace: "accessibility"
     description: "Adds an animation for when the FAB is displaced by an IME becoming visible."
@@ -28,4 +35,4 @@
     namespace: "accessibility"
     description: "Animates the floating menu's transition between curved and jagged edges."
     bug: "281140482"
-}
\ No newline at end of file
+}