Refactor GitHub Actions Caching

[alessfg]

Is your feature request related to a problem? Please describe

As of today, Docker builds are cached using the GitHub Actions cache. The current GitHub Actions caching solution does not take into account Docker image base layers containing updated packages, and does not let you define key names for the various cached layers, making it almost impossible to determine with cached shards correspond to each Docker image layer. This poses an issue when trying to selectively remove a cached Docker image layer due to, for example, outdated dependencies, or more importantly, CVEs. And means we might need to wipe the GitHub Actions cache before rebuilding any relevant images.

Describe the solution you'd like

• Being able to assign human readable names to each cached layer
• Dynamically delete outdated layers and rebuild the Docker images

Additional context

This issue is a follow up from #136 -- the original issue included improving the GitHub Actions cache support but on hindsight it makes more sense to track those efforts on a different issue.

Tasks

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1. Improve Docker layer cache naming
2. Wipe the GitHub Actions cache on critical alerts if there is a fix available for the CVE