Add selinux policies for traced_relay.relay_port sysprop

Define the traced_relay.relay_port sysprop as system internal
property and allowed traced_relay to read it. This property should only
be settable in debug builds.

Test: build perfetto in Android tree and use it
Bug: 393210308
Change-Id: I7f44eef6216cd83876f675737e288b9cab6905d1
diff --git a/private/property_contexts b/private/property_contexts
index fa82e29..0fd4399 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -88,6 +88,7 @@
 persist.security.       u:object_r:system_prop:s0
 persist.traced.enable   u:object_r:traced_enabled_prop:s0
 traced.lazy.            u:object_r:traced_lazy_prop:s0
+traced_relay.relay_port u:object_r:traced_relay_relay_port_prop:s0
 persist.heapprofd.enable u:object_r:heapprofd_enabled_prop:s0
 persist.traced_perf.enable u:object_r:traced_perf_enabled_prop:s0
 uprobestats.start_with_config u:object_r:uprobestats_start_with_config_prop:s0