Leave moved-from valueless after move and move assign when allocators don't compare equal

[jogerh]

N5032 specifies that move constructors and move assignment operators should leave the moved-from object in a valueless state.

https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/n5032.pdf

This patch fixes this when allocators don't compare equal

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.71%. Comparing base (0588bee) to head (d58038a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #622   +/-   ##
=======================================
  Coverage   98.71%   98.71%           
=======================================
  Files          14       14           
  Lines         855      859    +4     
  Branches       90       90           
=======================================
+ Hits          844      848    +4     
  Misses         11       11           

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[jbcoe]

This looks great modulo some linter issues.

I think that running pre-commit and adding // NOLINT for use-after-move in the test should suffice.

[jbcoe]

Thanks for the PR @jogerh

Do you make use of indirect or polymorphic in your code?

[jogerh]

Thanks for the PR @jogerh

Do you make use of indirect or polymorphic in your code?

Thank you for approving the PR! I am not using indirect or polymorphic yet, but I would really like to try it out. I initially considered it mostly for pimpl types, but now I see that most places where I use std::unique_ptr would benefit from indirect.

[jbcoe]

I'd be interested to see diffs if you are able to share. Thanks for the PRs!