Set bash -euo pipefail as default shell options in all github actions workflows

[grst]

We had it at least in the main test.yml script, but it got removed in #433, possibly as a mistake during resolution of a merge conflict.

defaults:
  run:
    # to fail on error in multiline statements (-e), in pipes (-o pipefail), and on unset variables (-u).
    shell: bash -euo pipefail {0}

@flying-sheep, any reason not do have this?

[flying-sheep]

It should be shell: bash, see here

I flip-flopped here because I think

1. I discovered that it’s not set, so I set it
2. I read that “bash” means that these options are included, so I removed it
3. I realized that only an explicit “bash” means that, not the default.

So the correct thing to do is probably shell: bash # https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#defaultsrunshell