DAOS-14679 pool: Debug ds_pool_child refs

[liw]

Introduce a simple type-checked vector template to gurt. See D_VEC_DECLARE and D_VEC_DEFINE for its usage.

Introduce a non-production reference tracker mechanism for debugging reference counting problems. See d_ref_tracker. Use this new mechanism for ds_pool_child. (See #14688 for more usage.)

This tracking is only compiled in for non-release builds; there should be no performance or memory overhead for release builds.

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• [ ] Two review approvals and any prior change requests have been resolved.
• [ ] Testing is complete and all tests passed or there is a reason documented in the PR why it should be force landed and forced-landing tag is set.
• [ ] Features: (or Test-tag*) commit pragma was used or there is a reason documented that there are no appropriate tags for this PR.
• [ ] Commit messages follows the guidelines outlined here.
• [ ] Any tests skipped by the ticket being addressed have been run and passed in the PR.

Gatekeeper:

• [ ] You are the appropriate gatekeeper to be landing the patch.
• [ ] The PR has 2 reviews by people familiar with the code, including appropriate owners.
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• [ ] Checkpatch issues are resolved. Pay particular attention to ones that will show up on future PRs.
• [ ] All builds have passed. Check non-required builds for any new compiler warnings.
• [ ] Sufficient testing is done. Check feature pragmas and test tags and that tests skipped for the ticket are run and now pass with the changes.
• [ ] If applicable, the PR has addressed any potential version compatibility issues.
• [ ] Check the target branch. If it is master branch, should the PR go to a feature branch? If it is a release branch, does it have merge approval in the JIRA ticket.
• [ ] Extra checks if forced landing is requested
  • [ ] Review comments are sufficiently resolved, particularly by prior reviewers that requested changes.
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• [ ] Fix the commit message upon landing. Check the standard here. Edit it to create a single commit. If necessary, ask submitter for a new summary.

[github-actions[bot]]

Ticket title is 'LRZ: dmg pool destroy fails' Status is 'Resolved' Labels: 'LRZ,scrubbed_2.8,triaged' Job should run at elevated priority (1) https://daosio.atlassian.net/browse/DAOS-14679