Moves create_all_accounts_run_and_snapshot_dirs() into accounts-db utils

[brooksprumo]

Problem

We're trying to remove the fs-err crate. For more information, please refer to #34838.

Basically the last hold-outs are in snapshot_utils. And while looking at the code, I saw that snapshot_utils::create_all_accounts_run_and_snapshot_dirs() et al just wrap functions inside accounts_db.rs, and then change the returned error type. Also strange, the test for this function is in snapshot_bank_utils.rs.

These functions are kind of for snapshots, but more for accounts-db. And there's no need for the wrapper functions. So lets have all the code and tests in a single location.

Summary of Changes

• Move the create_all_accounts_run_and_snapshot_dirs() et al functions into a new utils module within the accounts-db crate.
• Move the tests too
• Remove the wrapper functions in snapshot_utils.rs
• Update all the callers

Note that basically zero code was changed in the move. I did add constants for the "run" and "snapshot" string literals though.

This PR is a prereq to further cleanup snapshot_utils.rs.

[codecov]

Codecov Report

Attention: 36 lines in your changes are missing coverage. Please review.

Comparison is base (f9bfb60) 81.7% compared to head (b47229a) 81.6%.
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #34877     +/-   ##
=========================================
- Coverage    81.7%    81.6%   -0.2%     
=========================================
  Files         826      827      +1     
  Lines      223371   223788    +417     
=========================================
+ Hits       182578   182656     +78     
- Misses      40793    41132    +339     

[steviez]

LGTM