chore: revisit TODOs

[ShadowCurse]

Changes

Most TODOs are not actionable and are deleted. Remaining are left as is or updated.

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

• 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 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.23%. Comparing base (4132f64) to head (015347b).

Files with missing lines	Patch %	Lines
src/firecracker/src/metrics.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5652      +/-   ##
==========================================
- Coverage   83.23%   83.23%   -0.01%     
==========================================
  Files         277      277              
  Lines       29316    29311       -5     
==========================================
- Hits        24402    24397       -5     
  Misses       4914     4914              

Flag	Coverage Δ
5.10-m5n.metal	83.56% <83.33%> (-0.01%)	⬇️
5.10-m6a.metal	82.89% <83.33%> (+<0.01%)	⬆️
5.10-m6g.metal	80.28% <83.33%> (+<0.01%)	⬆️
5.10-m6i.metal	83.56% <83.33%> (+<0.01%)	⬆️
5.10-m7a.metal-48xl	82.89% <83.33%> (+<0.01%)	⬆️
5.10-m7g.metal	80.28% <83.33%> (+<0.01%)	⬆️
5.10-m7i.metal-24xl	83.53% <83.33%> (+<0.01%)	⬆️
5.10-m7i.metal-48xl	83.54% <83.33%> (+<0.01%)	⬆️
5.10-m8g.metal-24xl	80.27% <83.33%> (-0.01%)	⬇️
5.10-m8g.metal-48xl	80.27% <83.33%> (+<0.01%)	⬆️
6.1-m5n.metal	83.59% <83.33%> (+<0.01%)	⬆️
6.1-m6a.metal	82.92% <83.33%> (-0.02%)	⬇️
6.1-m6g.metal	80.27% <83.33%> (-0.01%)	⬇️
6.1-m6i.metal	83.58% <83.33%> (-0.01%)	⬇️
6.1-m7a.metal-48xl	82.91% <83.33%> (+<0.01%)	⬆️
6.1-m7g.metal	80.27% <83.33%> (-0.01%)	⬇️
6.1-m7i.metal-24xl	83.60% <83.33%> (+<0.01%)	⬆️
6.1-m7i.metal-48xl	83.60% <83.33%> (+<0.01%)	⬆️
6.1-m8g.metal-24xl	80.27% <83.33%> (-0.01%)	⬇️
6.1-m8g.metal-48xl	80.28% <83.33%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.