Problem: memiavl leave tmp directories behind

[mmsqe]

👮🏻👮🏻👮🏻 !!!! REFERENCE THE PROBLEM YOUR ARE SOLVING IN THE PR TITLE AND DESCRIBE YOUR SOLUTION HERE !!!! DO NOT FORGET !!!! 👮🏻👮🏻👮🏻

Closes: #1095

PR Checklist:

• Have you read the CONTRIBUTING.md?
• Does your PR follow the C4 patch requirements?
• Have you rebased your work on top of the latest master?
• Have you checked your code compiles? (make)
• Have you included tests for any non-trivial functionality?
• Have you checked your code passes the unit tests? (make test)
• Have you checked your code formatting is correct? (go fmt)
• Have you checked your basic code style is fine? (golangci-lint run)
• If you added any dependencies, have you checked they do not contain any known vulnerabilities? (go list -json -m all | nancy sleuth)
• If your changes affect the client infrastructure, have you run the integration test?
• If your changes affect public APIs, does your PR follow the C4 evolution of public contracts?
• If your code changes public APIs, have you incremented the crate version numbers and documented your changes in the CHANGELOG.md?
• If you are contributing for the first time, please read the agreement in CONTRIBUTING.md now and add a comment to this pull request stating that your PR is in accordance with the Developer's Certificate of Origin.

Thank you for your code, it's appreciated! :)

[codecov]

Codecov Report

Merging #1099 (c09896c) into main (50dc1d2) will increase coverage by 1.88%.
The diff coverage is 37.50%.

@@            Coverage Diff             @@
##             main    #1099      +/-   ##
==========================================
+ Coverage   46.48%   48.37%   +1.88%     
==========================================
  Files          81       65      -16     
  Lines        7221     5881    -1340     
==========================================
- Hits         3357     2845     -512     
+ Misses       3510     2722     -788     
+ Partials      354      314      -40     

Impacted Files	Coverage Δ
memiavl/db.go	57.53% <37.50%> (-0.47%)	⬇️

... and 23 files with indirect coverage changes

[yihuang]

Don't do pruning, just cleanup tmp dirs