Separate system_ext_mac_permissions.xml out of system sepolicy.

Bug: 137712473
Test: boot crosshatch
Test: Moving product sepolicy to system_ext and checks the file contents in
      /system_ext/etc/selinux are identical to previous contents in
      /product/etc/selinux.
Change-Id: I434e7f23a1ae7d01d084335783255330329c44e9
diff --git a/private/file_contexts b/private/file_contexts
index aa620fa..eec4a18 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -422,11 +422,12 @@
 /(system_ext|system/system_ext)/etc/passwd          u:object_r:system_passwd_file:s0
 /(system_ext|system/system_ext)/overlay(/.*)?       u:object_r:vendor_overlay_file:s0
 
-/(system_ext|system/system_ext)/etc/selinux/system_ext_file_contexts      u:object_r:file_contexts_file:s0
-/(system_ext|system/system_ext)/etc/selinux/system_ext_hwservice_contexts u:object_r:hwservice_contexts_file:s0
-/(system_ext|system/system_ext)/etc/selinux/system_ext_property_contexts  u:object_r:property_contexts_file:s0
-/(system_ext|system/system_ext)/etc/selinux/system_ext_seapp_contexts     u:object_r:seapp_contexts_file:s0
-/(system_ext|system/system_ext)/etc/selinux/system_ext_service_contexts   u:object_r:service_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_file_contexts        u:object_r:file_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_hwservice_contexts   u:object_r:hwservice_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_property_contexts    u:object_r:property_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_seapp_contexts       u:object_r:seapp_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_service_contexts     u:object_r:service_contexts_file:s0
+/(system_ext|system/system_ext)/etc/selinux/system_ext_mac_permissions\.xml u:object_r:mac_perms_file:s0
 
 #############################
 # Vendor files from /(product|system/product)/vendor_overlay