Improve metrics on batcher

[JulianVentura]

1. Metrics of failed batches: We only take into account a failed batch when the blockchain reverts, but no other failures, for instance an S3 connection failure.
2. Total proofs: We have a metric which "Total proofs received" which adds all received proofs, without taking into account if they succeed or not. We should provide more information and for this we have to add a new metric. We have two options:

• Total proofs failed: Sums all the proofs that were received but failed to be sucessfully included in a batch for some reason
• Total proofs sent: Sums up all the proofs that were successfully included in a batch and sent