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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check CONTRIBUTING.md.

PR Checklist

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

---

• [x] This functionality cannot be added in rust-vmm.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 85.71429% with 14 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 83.32%. Comparing base (7a45e88) to head (9a48a03).

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

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5528      +/-   ##
==========================================
- Coverage   83.38%   83.32%   -0.06%     
==========================================
  Files         277      277              
  Lines       28892    28884       -8     
==========================================
- Hits        24091    24069      -22     
- Misses       4801     4815      +14     

Flag	Coverage Δ
5.10-m5n.metal	83.55% <85.71%> (-0.06%)	:arrow_down:
5.10-m6a.metal	82.88% <85.71%> (-0.07%)	:arrow_down:
5.10-m6g.metal	80.25% <85.71%> (-0.07%)	:arrow_down:
5.10-m6i.metal	83.55% <85.71%> (-0.07%)	:arrow_down:
5.10-m7a.metal-48xl	82.87% <85.71%> (-0.07%)	:arrow_down:
5.10-m7g.metal	80.25% <85.71%> (-0.07%)	:arrow_down:
5.10-m7i.metal-24xl	83.52% <85.71%> (-0.07%)	:arrow_down:
5.10-m7i.metal-48xl	83.52% <85.71%> (-0.06%)	:arrow_down:
5.10-m8g.metal-24xl	80.25% <85.71%> (-0.07%)	:arrow_down:
5.10-m8g.metal-48xl	80.24% <85.71%> (-0.07%)	:arrow_down:
6.1-m5n.metal	?
6.1-m6a.metal	82.91% <85.71%> (-0.07%)	:arrow_down:
6.1-m6g.metal	80.25% <85.71%> (-0.06%)	:arrow_down:
6.1-m6i.metal	83.58% <85.71%> (-0.07%)	:arrow_down:
6.1-m7a.metal-48xl	82.90% <85.71%> (-0.06%)	:arrow_down:
6.1-m7g.metal	80.25% <85.71%> (-0.07%)	:arrow_down:
6.1-m7i.metal-24xl	83.59% <85.71%> (-0.06%)	:arrow_down:
6.1-m7i.metal-48xl	83.59% <85.71%> (-0.07%)	:arrow_down:
6.1-m8g.metal-24xl	80.25% <85.71%> (-0.06%)	:arrow_down:
6.1-m8g.metal-48xl	80.25% <85.71%> (-0.06%)	:arrow_down:

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