Research stable vs nightly Rust channels and decide what to use in github actions for the projects

[soenkeliebau]

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[soenkeliebau]

l've looked into this a little bit when starting the review of Lars' PR for the zookeeper operator, as I stumbled across his use of the nightly toolchain right of the bat.

https://stackoverflow.com/a/56067977/7183757
https://www.reddit.com/r/rust/comments/gn3iwf/how_stableunstable_is_nightly/
https://blog.datalust.co/our-journey-from-rust-nightly-to-stable/
https://news.ycombinator.com/item?id=13251729

The general consensus seems to be that nightly is fairly stable and people do use it in production, as anything that goes in it is extensively tested. Anything that breaks prior working things do not go into master/main. But of course no one will ever straight up say "yes it is stable enough for production".
However this does not mean that stuff might change abruptly in nightly, so if we always use the latest available nightly version we run the risk of a build working one day and failing the next (not a huge risk, but a possibility).

The big issue in our case is the backtrace feature, which is not in stable yet - if we want that we need to run nightly.

Maybe as a compromise we can agree to use a fixed version of nightly for our builds and update that every few weeks or so. That way at least it will be a conscious decision to upgrade and we know to watch the next builds closely.

I'd still prefer if we moved to stable at some point though.