Whitelist exported platform properties

This CL lists all the exported platform properties in
private/exported_property_contexts.

Additionally accessing core_property_type from vendor components is
restricted.
Instead public_readable_property_type is used to allow vendor components
to read exported platform properties, and accessibility from
vendor_init is also specified explicitly.

Note that whitelisting would be applied only if
PRODUCT_COMPATIBLE_PROPERTY is set on.

Bug: 38146102
Test: tested on walleye with PRODUCT_COMPATIBLE_PROPERTY=true
Change-Id: I304ba428cc4ca82668fec2ddeb17c971e7ec065e
diff --git a/private/surfaceflinger.te b/private/surfaceflinger.te
index f28e3fe..694bb2f 100644
--- a/private/surfaceflinger.te
+++ b/private/surfaceflinger.te
@@ -46,6 +46,9 @@
 
 # Set properties.
 set_prop(surfaceflinger, system_prop)
+set_prop(surfaceflinger, exported_system_prop)
+set_prop(surfaceflinger, exported2_system_prop)
+set_prop(surfaceflinger, exported3_system_prop)
 set_prop(surfaceflinger, ctl_bootanim_prop)
 
 # Use open files supplied by an app.