Add features used by puya-ts back into shared config

[tristanmenzel]

• Ability to publish an artifact after building and download published artifacts of other jobs before building
• Ability to set up a python version in case a python utility is used to build the project
• Add a post build script step

[robdmoore]

I'm not sure these changes make sense to merge. The need for Python in a node.js project is a bit specific (and we have other dedicated python ones) and the ci one isn't meant to have artifact publishing since usually you need to run build for that and we have workflows designed to do that. Closing for now, but feel free to re-open if I've misunderstood something?