build: Speed up docker build in some setups

[abador]

This change adds builder cache in dockerfile. This speeds up the build in some cases.

Related issue(s)

Checklist

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  introduces a new feature.
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Further Comments

[aeneasr]

Could you please link some docs explaining how this works? Thank you :)

[abador]

This change is basically a way to add caching to our docker builds on a local machine that runs that build. If you run it on a different machine there is no difference. I also split this into a multi-stage build (this also might speed some things up). Some example doc about this: https://www.docker.com/blog/containerize-your-go-developer-environment-part-2/

[aeneasr]

Is this needed?

[abador]

As far as I know this changes the way dockerfiles are parsed and it's still needed in the current version

[aeneasr]

We are using the same image as in the previous step, do we need to or can we leave this out?

[abador]

it will still work porperly without this