ledger-tool: Add an analysis-account command

[mvines]

It's difficult to gain insight into the current population of accounts in the ledger. Some useful information would be

• a histogram of account sizes
• breakdown of number of accounts by owner
• hot/cold accounts

This information could support future work of optimizing snapshot generation and account management as the account set grows. A devnet snapshot is over 1 GB right now, and is likely a forebearer of things to come on testnet and mainnet-beta.

[ryoqun]

Also, this could add total supply and distribution grouped by each spl token type.

[jstarry]

@mvines what does hot/cold accounts mean?

[mvines]

Accounts access frequency. Vote account is hot, some stake account that hasn't moved since genesis pretty cold. One day I imagine we'd move cold accounts into slower storage or even take them offline entirely, and require a "reactivate" or "ping" instruction to warm them back up again.