#### Problem
Having a PR that is self-contained with a big picture while having it testable
for TieredStorage::write_accounts is challenging, as it requires all the write-side
code, read-side code, and test code.
#### Summary of Changes
This PR solves part of the problem by having one dedicated PR for tests.
Specifically, it includes test utils that allow us to generate test accounts,
invoke write_accounts, and verify the written tiered-storage instance.
With this PR, it will be easier to write future PRs.
#### Test Plan
A new set of unit-tests and test utils is included in this PR.
When a consensus divergance occurs, the current workflow involves a
handful of manual steps to hone in on the offending slot and
transaction. This process isn't overly difficult to execute; however, it
is tedious and currently involves creating and parsing logs.
This change introduces functionality to output a debug file that
contains the components go into the bank hash. The file can be generated
in two ways:
- Via solana-validator when the node realizes it has diverged
- Via solana-ledger-tool verify by passing a flag
When a divergance occurs now, the steps to debug would be:
- Grab the file from the node that diverged
- Generate a file for the same slot with ledger-tool with a known good
version
- Diff the files, they are pretty-printed json