Add persist.sysui.notification.builder_extras_ovrd

Adds persist.sysui.notification.builder_extras_override property
and associated permissions, which will be used to flag guard
a change in core/...Notification.java.

Permissions are limited in scope to avoid unnecessary access.
Apps may need to read the flag (because Notification.java
is a core library), but setting should only be possible
internally (and via debug shell).

Test: manual flash+adb setprop/getprop
Bug: 169435530
Change-Id: I3f7e2220798d22c90f4326570732a52b0deeb54d
diff --git a/private/property.te b/private/property.te
index 9e49c30..1fdba27 100644
--- a/private/property.te
+++ b/private/property.te
@@ -54,6 +54,7 @@
 # Properties which can't be written outside system
 system_restricted_prop(device_config_virtualization_framework_native_prop)
 system_restricted_prop(log_file_logger_prop)
+system_restricted_prop(persist_sysui_builder_extras_prop)
 
 ###
 ### Neverallow rules