Separate system_ext_seapp_contexts out of system sepolicy.

Bug: 137712473
Test: boot crosshatch
Change-Id: I2c2acbcf234861feb39834c867a4eb74c506692d
diff --git a/private/file_contexts b/private/file_contexts
index 8d4e6bc..a6c4edd 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -423,6 +423,7 @@
 /(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_seapp_contexts u:object_r:seapp_contexts_file:s0
 
 #############################
 # Vendor files from /(product|system/product)/vendor_overlay