Add libgui bq_consumer_attach_callback flag

Add a flag for enabling IProducerListener callback when the consumer
attaches a buffer.

Bug: 353202582
Flag: EXEMPT adding flag
Test: n/a
Change-Id: I3268cb82fdc7d194f8b1864b8a72147ff51e3973
diff --git a/libs/gui/libgui_flags.aconfig b/libs/gui/libgui_flags.aconfig
index c79a2b7..fdc657e 100644
--- a/libs/gui/libgui_flags.aconfig
+++ b/libs/gui/libgui_flags.aconfig
@@ -75,3 +75,11 @@
   bug: "354273690"
   is_fixed_read_only: true
 } # wb_surface_connect_methods
+
+flag {
+  name: "bq_consumer_attach_callback"
+  namespace: "core_graphics"
+  description: "Controls IProducerListener to have consumer side attach callback"
+  bug: "353202582"
+  is_fixed_read_only: true
+} # bq_consumer_attach_callback