Generate nightly builds and json files

[alvicsam]

PR adds a nightly release pipeline.
Since the logic for the nightly build and release differs significantly from the usual pipeline, I decided to put it in a separate file. The same applies to the Python script that generates JSON files.

The nightly pipeline runs at 01:00 UTC every day, producing artefacts and retaining them for 40 days if commits are made the day before it runs.

cc #355
cc https://github.com/paritytech/devops/issues/4141

[xermicus]

Thank you @alvicsam!

[xermicus]

In theory the nightly release should just have different commit inputs right? Then no actual build logic needs to be duplicated. I see a lot of duplicated code in release-nightly.yml - for maintainability I'd appreciate making release.yml more modular (maybe as it's own GH actions or even a couple ones). WDYT?

[alvicsam]

In theory the nightly release should just have different commit inputs right?

In theory, yes, and the build jobs are the same, but the logic for working with artifacts differs. I tried to keep everything in one pipeline. However, there were too many rules about whether a job or step should run, which made the pipeline definition difficult to read.

We could merge this one so it starts producing nightly builds and do the refactor later. WDYT?

[xermicus]

Maybe the rules could be modularized too?

I am fine with merging it to simplify trying it out - if you promise to improve it afterwards :)

[alvicsam]

AFAIK no, it's not applicable to the rules. I'll create a separate issue then for the refactor.