[hwc-batching] Surfaceflinger code for HWC batching support.

This CL adds the SurfaceFlinger side code for supporting the new
batched commands for createLayer/DestroyLayer.

Bug: 290685621
Test: atest VtsHalGraphicsComposer3_TargetTest
      atest PerInstance/GraphicsComposerAidlBatchedCommandTest
Change-Id: I1793bda0a1eac1c2cecd0c6ab00d5df9fd8d6d0a
diff --git a/services/surfaceflinger/surfaceflinger_flags.aconfig b/services/surfaceflinger/surfaceflinger_flags.aconfig
index 3f26448..1a28b81 100644
--- a/services/surfaceflinger/surfaceflinger_flags.aconfig
+++ b/services/surfaceflinger/surfaceflinger_flags.aconfig
@@ -32,6 +32,14 @@
 }
 
 flag {
+  name: "enable_layer_command_batching"
+  namespace: "core_graphics"
+  description: "This flag controls batching on createLayer/destroyLayer command with executeCommand."
+  bug: "290685621"
+  is_fixed_read_only: true
+}
+
+flag {
   name: "dont_skip_on_early"
   namespace: "core_graphics"
   description: "This flag is guarding the behaviour where SurfaceFlinger is trying to opportunistically present a frame when the configuration change from late to early"