feat: support insert if not exists async

[MrCroxx]

What's changed and what's your intention?

Please explain IN DETAIL what the changes are in this PR and why they are needed. :D

As titled.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have passed make check and make test or make all in my local envirorment.

Related issues or PRs (optional)

[codecov]

Codecov Report

Merging #212 (78e25d4) into main (4c32fe1) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

❗ Current head 78e25d4 differs from pull request most recent head b97e9d8. Consider uploading reports for the commit b97e9d8 to get more accurate results

@@            Coverage Diff             @@
##             main     #212      +/-   ##
==========================================
- Coverage   77.47%   77.44%   -0.03%     
==========================================
  Files          50       50              
  Lines        5815     5817       +2     
==========================================
  Hits         4505     4505              
- Misses       1310     1312       +2     

Files	Coverage Δ
foyer-storage/src/storage.rs	1.19% <0.00%> (-0.03%)	⬇️