wip,draft: Add async support to persist_test_utils

[ValuedMammal]

Description

Expands persist_test_utils module by adding a function persist_wallet_changeset_async to be used for testing an AsyncWalletPersister implementation. For now this is still WIP.

Notes to the reviewers

Changelog notice

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[codecov]

Codecov Report

❌ Patch coverage is 44.86692% with 145 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.43%. Comparing base (35502e0) to head (bf0057f).

Files with missing lines	Patch %	Lines
src/persist_test_utils.rs	44.86%	145 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #343      +/-   ##
==========================================
- Coverage   86.46%   85.43%   -1.04%     
==========================================
  Files          25       25              
  Lines        8527     8649     +122     
==========================================
+ Hits         7373     7389      +16     
- Misses       1154     1260     +106     

Flag	Coverage Δ
rust	85.43% <44.86%> (-1.04%)	⬇️

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[ValuedMammal]

@110CodingP I changed this by removing the &Path arg from the create_stores Fn, which means this function is no longer in control of the path in which the stores are created. After thinking about it I'm not sure this is a feature that needs to be tested. Any thought about whether to keep or improve it somehow?