Migrate screenshot methods to AIDL

A new service, SurfaceFlingerAIDL, is added to surfaceflinger during
the process of mirgrating ISurfaceComposer interface to AIDL.
Once migration is complete, this service will be deleted.

Bug: 211037638
Test: screencap

Change-Id: I0e41700b1af1f482cda6a6d6c67b057553485cfd
diff --git a/private/service_contexts b/private/service_contexts
index 2e79abb..70b92e3 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -307,6 +307,7 @@
 storaged_pri                              u:object_r:storaged_service:s0
 storagestats                              u:object_r:storagestats_service:s0
 SurfaceFlinger                            u:object_r:surfaceflinger_service:s0
+SurfaceFlingerAIDL                        u:object_r:surfaceflinger_service:s0
 suspend_control                           u:object_r:system_suspend_control_service:s0
 suspend_control_internal                  u:object_r:system_suspend_control_internal_service:s0
 system_config                             u:object_r:system_config_service:s0