Record app optimization mode backup into BatteryHistoricalLog

App optimization mode format:
https://screenshot.googleplex.com/di9DDzBfYf7ihfV

App optimization mode backup format:
https://screenshot.googleplex.com/GkVW5HrgGvmv5yh

Bug: 192523697
Test: make SettingsRoboTests
Change-Id: I60a9a76a8ffc89d625ee3f77c138a19181c81c38
diff --git a/protos/fuelgauge_log.proto b/protos/fuelgauge_log.proto
index cf87dc7..8512cb8 100644
--- a/protos/fuelgauge_log.proto
+++ b/protos/fuelgauge_log.proto
@@ -19,10 +19,11 @@
     APPLY = 2;
     RESET = 3;
     RESTORE = 4;
+    BACKUP = 5;
   }
 
   optional string package_name = 1;
   optional Action action = 2;
   optional string action_description = 3;
   optional int64 timestamp = 4;
-}
\ No newline at end of file
+}