SnapshotMergeReported: add retrofit and cow image size

Additional information are important to evaluate the impact of Virtual
A/B on devices especially related to OTA take rate.
Take rate is strictly related to the space that is temporarily allocated
in the /data partition (cow_file_size_bytes), as well as knowing if the
device has been upgraded to use Virtual A/B (is_vab_retrofit) or if the
feature was natively supported.
Add these new fields to the SnapshotMergeReported metric.

Bug: 154016862
Bug: 157720191
Test: m
Signed-off-by: Alessio Balsini <balsini@google.com>
Change-Id: Iae8310a8f5364ee94fc8ad6e55362d86cb0752d8
diff --git a/cmds/statsd/src/atoms.proto b/cmds/statsd/src/atoms.proto
index c25c3db..c474e71 100644
--- a/cmds/statsd/src/atoms.proto
+++ b/cmds/statsd/src/atoms.proto
@@ -4860,6 +4860,14 @@
     // Number of reboots that occurred after issuing and before completing the
     // merge of all the snapshot devices.
     optional int32 intermediate_reboots = 3;
+
+    // The device has been upgraded to Virtual A/B.
+    optional bool is_vab_retrofit = 4;
+
+    // Space that has been temporarily allocated in the /data partition
+    // containing the dm-snapshot's copy-on-write data generated during a
+    // Virtual A/B update.
+    optional int64 cow_file_size_bytes = 5;
 }
 
 //////////////////////////////////////////////////////////////////////