Minimize public policy

Ideally, public should only contain APIs (types / attributes) for
vendor. The other statements like allow/neverallow/typeattributes are
regarded as implementation detail for platform and should be in private.

Bug: 232023812
Test: m selinux_policy
Test: diff <(git diff --staged | grep "^-" | cut -b2- | sort) \
           <(git diff --staged | grep "^+" | cut -b2- | sort)
Test: remove comments on plat_sepolicy.cil, replace base_typeattr_*
      to base_typeattr and then compare old and new plat_sepolicy.cil
Change-Id: I5e7d2da4465ab0216de6bacdf03077d37f6ffe12
diff --git a/private/service.te b/private/service.te
index cce3be4..d777e53 100644
--- a/private/service.te
+++ b/private/service.te
@@ -33,3 +33,12 @@
 
 type uce_service,                   service_manager_type;
 type wearable_sensing_service,      app_api_service, system_server_service, service_manager_type;
+
+###
+### Neverallow rules
+###
+
+# servicemanager handles registering or looking up named services.
+# It does not make sense to register or lookup something which is not a service.
+# Trigger a compile error if this occurs.
+neverallow domain ~{ service_manager_type vndservice_manager_type }:service_manager { add find };