[virtio-mem] chore(pci): gracefully handle errors in the PCI restore code

[Manciukic]

Changes

All errors were previously unwrapped, differently from MMIO where they were handled. Refactor the code to handle the errors in the same way as MMIO.

Reason

unify MMIO and PCI persist logic.

License Acceptance

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CONTRIBUTING.md.

PR Checklist

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkbuild --all to verify that the PR passes
  build checks on all supported architectures.
• I have run tools/devtool checkstyle to verify that the PR passes the
  automated style checks.
• I have described what is done in these changes, why they are needed, and
  how they are solving the problem in a clear and encompassing way.
• I have updated any relevant documentation (both in code and in the docs)
  in the PR.
• I have mentioned all user-facing changes in CHANGELOG.md.
• If a specific issue led to this PR, this PR closes the issue.
• When making API changes, I have followed the
  Runbook for Firecracker API changes.
• I have tested all new and changed functionalities in unit tests and/or
  integration tests.
• I have linked an issue to every new TODO.

---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.27%. Comparing base (c37849c) to head (ccdb655).

Files with missing lines	Patch %	Lines
src/vmm/src/device_manager/pci_mngr.rs	85.10%	14 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                   @@
##           feature/virtio-mem    #5528      +/-   ##
======================================================
- Coverage               83.32%   83.27%   -0.06%     
======================================================
  Files                     276      276              
  Lines                   28823    28815       -8     
======================================================
- Hits                    24018    23996      -22     
- Misses                   4805     4819      +14     

Flag	Coverage Δ
5.10-m5n.metal	83.49% <85.71%> (-0.07%)	⬇️
5.10-m6a.metal	82.80% <85.71%> (-0.07%)	⬇️
5.10-m6g.metal	80.25% <85.71%> (-0.07%)	⬇️
5.10-m6i.metal	83.48% <85.71%> (-0.06%)	⬇️
5.10-m7a.metal-48xl	82.79% <85.71%> (-0.07%)	⬇️
5.10-m7g.metal	80.24% <85.71%> (-0.07%)	⬇️
5.10-m7i.metal-24xl	83.46% <85.71%> (-0.06%)	⬇️
5.10-m7i.metal-48xl	83.46% <85.71%> (-0.07%)	⬇️
5.10-m8g.metal-24xl	80.25% <85.71%> (-0.07%)	⬇️
5.10-m8g.metal-48xl	80.24% <85.71%> (-0.07%)	⬇️
6.1-m5n.metal	83.52% <85.71%> (-0.06%)	⬇️
6.1-m6a.metal	82.83% <85.71%> (-0.07%)	⬇️
6.1-m6g.metal	80.24% <85.71%> (-0.07%)	⬇️
6.1-m6i.metal	83.51% <85.71%> (-0.07%)	⬇️
6.1-m7a.metal-48xl	82.82% <85.71%> (-0.07%)	⬇️
6.1-m7g.metal	80.24% <85.71%> (-0.07%)	⬇️
6.1-m7i.metal-24xl	83.52% <85.71%> (-0.07%)	⬇️
6.1-m7i.metal-48xl	83.53% <85.71%> (-0.06%)	⬇️
6.1-m8g.metal-24xl	80.24% <85.71%> (-0.07%)	⬇️
6.1-m8g.metal-48xl	80.24% <85.71%> (-0.07%)	⬇️

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