* Add run parent directory for accounts files
* fix test test_concurrent_snapshot_packaging
* review comments. renamed the path setup function
* Addressed most of the review comments
* remove explict type def for map result
* handle create_accounts_run_and_snapshot_dirs error with expect
* update with more review comments
* minor fixes from review comments
* simplify account_filename option assignment
* handle error from create_accounts_run_and_snapshot_dirs
* use then instead of then_some for lazy evaluation
* Clean up files in the old account_path before trasitioning to the new run path
* try_exist and accounts_dir removing extra
* sync rmdir, is_dir check
* handle the account_path not deletable case
* Add run parent directory for accounts files
* fix test test_concurrent_snapshot_packaging
* review comments. renamed the path setup function
* Addressed most of the review comments
* remove explict type def for map result
* handle create_accounts_run_and_snapshot_dirs error with expect
* update with more review comments
* minor fixes from review comments
* simplify account_filename option assignment
* handle error from create_accounts_run_and_snapshot_dirs
* use then instead of then_some for lazy evaluation
* Add entry_processor fn to unpack_archive - not used yet
* Add generic unpack_snapshot_with_processors to separate account paths handling from entry checking
#### Summary of Changes
To avoid mixing the use of different shred storage types, each shred storage type
will have its blockstore in a different directory.
This PR still keeps the RocksFifo setting hidden. The default ShredStorageType and
blockstore directory are still RocksLevel and `rocksdb`.
Will follow-up with PRs on making FIFO option public in ledger-tool and validator.
#### Test Plan
* Added a new test to verify the existence of `rocksdb-fifo` directory when FIFO compaction is used.
* Updated existing test to verify the current setting still store ledger under `rocksdb` directory.
* Manually ran ledger_cleanup_test with both level and fifo compaction and verified the resulting ledger.
* Ran a validator with this PR.
Refactor a few functions that are on the load-from-snapshot path, to facilitate
adding in incremental snapshots more easily.
Additionally, add some tests and doc comments.