[Feature] Adding DB usage metrics to SnarkVM

[miazn]

🚀 Feature

As discussed with @vicsn and @niklaslong , it might be useful to expose metrics on DB writes/reads from SnarkVM to be scraped by Prometheus

Motivation

To better debug/diagnose latency in the network/nodes

Implementation

Add metrics (most likely latency histograms) to the ledger/store/src/helpers/rocksdb Map atomic read/write methods