Add new keystore2 permission get_last_auth_time.

This is checked when getting the time of last successful authentication
from keystore2. The auth_service is the only expected caller.

Bug: 303839446
Test: manual
Change-Id: Idf222e69c0553a7be94206b519a95a4006e69507
diff --git a/private/system_server.te b/private/system_server.te
index efdeff4..aa95dce 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -979,6 +979,7 @@
 	change_user
 	clear_ns
 	clear_uid
+	get_last_auth_time
 	lock
 	pull_metrics
 	reset