Do not drop AppendVec in store-tool

[brooksprumo]

Problem

The store-tool should remove cause the backing storage of the AppendVec it inspects to be removed. Currently, that's accomplished via toggling the AppendVec::remove_on_drop field. Now that Rust has ManuallyDrop, we can (i.e. should) use that instead.

Summary of Changes

Use ManuallyDrop to not remove the backing store.

Miscellaneous

Here's an example of using ManuallyDrop, create a wrapper to not drop, and then another wrapper than can drop. Useful if ManuallyDrop is new-to-you: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=c5322f69ab160d2d557162f6c325a29e

[yhchiang-sol]

Neat! Thanks for spotting this!

[codecov]

Codecov Report

Merging #32739 (777ec0f) into master (533f42d) will increase coverage by 0.0%.
Report is 10 commits behind head on master.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #32739   +/-   ##
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  Coverage    81.9%    82.0%           
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  Files         784      784           
  Lines      211004   211004           
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+ Hits       173012   173029   +17     
+ Misses      37992    37975   -17