Problem: memiavl has resource leaks

[yihuang]

Solution:

• add defers and close functions

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

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 #1075 (80df52d) into main (368524d) will increase coverage by 24.40%.
The diff coverage is 71.42%.

@@             Coverage Diff             @@
##             main    #1075       +/-   ##
===========================================
+ Coverage   21.67%   46.08%   +24.40%     
===========================================
  Files          50       82       +32     
  Lines        3031     7139     +4108     
===========================================
+ Hits          657     3290     +2633     
- Misses       2310     3498     +1188     
- Partials       64      351      +287     

Impacted Files	Coverage Δ
memiavl/export.go	57.95% <55.55%> (ø)
memiavl/import.go	65.28% <100.00%> (ø)

... and 45 files with indirect coverage changes

[mmsqe]

should we add close this one as well

[yihuang]

should we add close this one as well

no, the snapshot is passed to the Trees, which will close them when the trees are closed.