chore: update docker image

[jonas-jonas]

This PR introduces multiple changes:

• updates node to 20
• updates ruby to 2.7 (this should unblock the release pipeline)
• updates dart 3.3
• adds a new script that fetches a dart version that matches the platform architecture to enable building this image on m1 (arm) macs.
• updates the base image to debian bullseye
• introduces a new PR workflow, that builds the image, runs the generate.sh & test.sh scripts and then provides the resulting image as a downloadable tarball for local use if the Dockerfile changed.

Related Issue or Design Document

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• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
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• I have added tests that prove my fix is effective or that my feature works.
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