Ledger tool print account size and load us

[tao-stones]

Problem

Hack ledger tool to replay MNB snapshots to investigate slow loading issue.

Slow loading issue: blocks, or transactions, spent a lot of timing in loading accounts, result load_usin replay metrics spike. (example slots: [170618100, 170618350])
Possible causes:

1. certain type accounts might be slow to load, say large size
2. too many accounts in a TX, and too many such TXs, cause overall load time spikes.

ran hacked ledger-tool on above slots range's snapshot, not finding evidences for case #1. In fact, the slowest laoded accounts are just random program accounts (including vote, ComputeBudget etc builtin programs).

Summary of Changes

Fixes #