proto: add new metrics for newlog

Add new metrics for newlog:
- totalSizeLogs: total size of logs on device
- oldestSavedDeviceLog: timestamp of the latest device log saved on
device

Signed-off-by: Paul Gaiduk <paulg@zededa.com>

proto/metrics/metrics.proto

@@ -655,6 +655,10 @@ message newlogMetric {
   uint32 tooManyRequest = 21;
   // counter for gzip files bypassing the uploading to cloud
   uint32 skipUploadAppFile = 22;
+  // total size of logs on device
+  uint64 totalSizeLogs = 23;
+  // timestamp of the latest device log saved on device
+  google.protobuf.Timestamp oldestSavedDeviceLog = 24;
 }
 
 // logfileMetrics - is shared for both device log and application log