chore: pythonify BK definitions for docker and coverage

[Manciukic]

Changes

Define Docker and Coverage pipelines in .buildkite folder as all other pipelines.

Reason

I wanted to remove c5n from all pipelines and found out these 2 pipelines are defined directly on BK website.
Let's move them to python as all the others so that they stay in sync with the latest and greatest updates to the supported platforms and instance types.

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.73%. Comparing base (0b2fd57) to head (371a2de).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5412      +/-   ##
==========================================
+ Coverage   82.69%   82.73%   +0.03%     
==========================================
  Files         263      263              
  Lines       27455    27455              
==========================================
+ Hits        22705    22715      +10     
+ Misses       4750     4740      -10     

Flag	Coverage Δ
5.10-c5n.metal	?
5.10-m5n.metal	82.84% <ø> (+<0.01%)	⬆️
5.10-m6a.metal	82.08% <ø> (-0.01%)	⬇️
5.10-m6g.metal	79.52% <ø> (ø)
5.10-m6i.metal	82.83% <ø> (ø)
5.10-m7a.metal-48xl	82.08% <ø> (?)
5.10-m7g.metal	79.52% <ø> (ø)
5.10-m7i.metal-24xl	82.81% <ø> (?)
5.10-m7i.metal-48xl	82.81% <ø> (?)
5.10-m8g.metal-24xl	79.52% <ø> (?)
5.10-m8g.metal-48xl	79.52% <ø> (?)
6.1-m5n.metal	82.88% <ø> (+<0.01%)	⬆️
6.1-m6a.metal	82.12% <ø> (ø)
6.1-m6g.metal	79.51% <ø> (-0.01%)	⬇️
6.1-m6i.metal	82.87% <ø> (ø)
6.1-m7a.metal-48xl	82.12% <ø> (?)
6.1-m7g.metal	79.52% <ø> (ø)
6.1-m7i.metal-24xl	82.88% <ø> (?)
6.1-m7i.metal-48xl	82.88% <ø> (?)
6.1-m8g.metal-24xl	79.52% <ø> (?)
6.1-m8g.metal-48xl	79.52% <ø> (?)

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[Manciukic]

• Docker popular container test: https://buildkite.com/firecracker/mancio-at-docker-poular-containers/builds/5
• Coverage test: https://buildkite.com/firecracker/mancio-at-run-coverage-dot-py-on-merge/builds/2