Use workflow to release firecracker instead

[djeebus]

No description provided.

[cursor]

PR Summary

Medium Risk
Changes the release automation path (tagging, uploading to GCS, and GitHub release assets) and introduces new validation logic, so misconfiguration could impact published binaries or skip needed builds.

Overview
Switches from the previous push-driven, firecracker_versions.txt matrix build to a manual release.yml workflow that resolves a tag/commit, checks CI status, detects existing artifacts in GCS/GitHub Releases, and only builds missing amd64/arm64 binaries before uploading.

Adds scripts/validate.py (with pytest coverage + a new Tests workflow and Poetry tooling) to perform the input/CI/artifact checks, and simplifies build.sh to build directly from a commit hash and write only the per-arch output layout. Updates docs/tooling (README.md, .tool-versions, .gitignore) and removes the old workflows and parsing/CI-check scripts.

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[ValentaTomas]

lgtm

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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