Relabel various exported3_default_prop

This removes bad context names "exported*_prop". Property contexts of
following properties are changed. All properties are settable only by
vendor-init.

- ro.config.per_app_memcg
This becomes lmkd_config_prop.

- ro.zygote
This becomes dalvik_config_prop.

- ro.oem_unlock_supported
This becomes oem_unlock_prop. It's readable by system_app which includes
Settings apps.

- ro.storage_manager.enabled
This becomes storagemanagr_config_prop. It's readable by coredomain.
Various domains in coredomain seem to read it.

- sendbug.preferred.domain
This bcomes sendbug_config_prop. It's readable by appdomain.

There are still 3 more exported3_default_prop, which are going to be
tracked individually.

Bug: 155844385
Test: selinux denial check on Pixel devices
Change-Id: I340c903ca7bda98a92d0f157c65f6833ed00df05
diff --git a/private/system_app.te b/private/system_app.te
index e160ff4..c2dc2d1 100644
--- a/private/system_app.te
+++ b/private/system_app.te
@@ -153,6 +153,9 @@
 allow system_app system_server:udp_socket {
         connect getattr read recvfrom sendto write getopt setopt };
 
+# Settings app reads ro.oem_unlock_supported
+get_prop(system_app, oem_unlock_prop)
+
 ###
 ### Neverallow rules
 ###