Updated CONTRIBUTING and getting-started docs

[seafoodfry]

Changes

1. Added some extra commands to ensure the kvm linux group is configured.
2. Added documentation detailing a way to make use of the ./tools/devctr poetry project for the pre-commit.
3. Added a .python-version file to help the installation of the poetry project which supports python versions 3.10.*

Reason

Had to figure out these details while getting started. Figured I should try contributing this info back into the project.

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

• [ ] If a specific issue led to this PR, this PR closes the issue.
• [x] The description of changes is clear and encompassing.
• [x] Any required documentation changes (code and docs) are included in this PR.
• [ ] API changes follow the Runbook for Firecracker API changes.
• [ ] User-facing changes are mentioned in CHANGELOG.md.
• [ ] All added/changed functionality is tested.
• [ ] New TODOs link to an issue.
• [x] Commits meet contribution quality standards.

---

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.34%. Comparing base (e67b2be) to head (3cd0d1b). Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4744   +/-   ##
=======================================
  Coverage   84.34%   84.34%           
=======================================
  Files         249      249           
  Lines       27461    27461           
=======================================
  Hits        23162    23162           
  Misses       4299     4299           

Flag	Coverage Δ
5.10-c5n.metal	84.57% <ø> (ø)
5.10-m5n.metal	84.55% <ø> (-0.01%)	:arrow_down:
5.10-m6a.metal	83.84% <ø> (ø)
5.10-m6g.metal	80.91% <ø> (ø)
5.10-m6i.metal	84.54% <ø> (ø)
5.10-m7g.metal	80.91% <ø> (ø)
6.1-c5n.metal	84.57% <ø> (ø)
6.1-m5n.metal	84.55% <ø> (-0.01%)	:arrow_down:
6.1-m6a.metal	83.84% <ø> (-0.01%)	:arrow_down:
6.1-m6g.metal	80.91% <ø> (ø)
6.1-m6i.metal	84.54% <ø> (ø)
6.1-m7g.metal	80.91% <ø> (ø)

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[seafoodfry]

Forced push to rebase with the latest from upstream/main (and because I forgot to cleanup one of the github-style footnotes).

[seafoodfry]

Thank you again for the reviews @roypat and @pb8o ! I squashed the commits.