Add per-bucket Entry size Metrics #4426
Description
Currently, we only track the size of the whole BucketList. This doesn't give us much insight into the makeup of the BucketList. We should add a size and count metric grouped by LedgerEntry type (and persistent vs. temporary for soroban types) to each Bucket. This could be efficiently calculated during Bucket merges. We should then aggregate BucketList level metrics and log these to grafana, as well as output them in meta.