bootstat: enhance last reboot reason property with file backing

Helps with support of recovery and rollback boot reason history, by
also using /metadata/bootstat/persist.sys.boot.reason to file the
reboot reason.  For now, label this file metadata_bootstat_file.

Test: manual
Bug: 129007837
Change-Id: Id1d21c404067414847bef14a0c43f70cafe1a3e2
diff --git a/private/compat/26.0/26.0.ignore.cil b/private/compat/26.0/26.0.ignore.cil
index 51e7b5c..73fb877 100644
--- a/private/compat/26.0/26.0.ignore.cil
+++ b/private/compat/26.0/26.0.ignore.cil
@@ -118,6 +118,7 @@
     mediaswcodec_tmpfs
     mediaextractor_update_service
     mediaprovider_tmpfs
+    metadata_bootstat_file
     metadata_file
     mnt_product_file
     mnt_vendor_file