ci: implement unified sections
Preparation part: use bash
where it's possible. Do not complicate life with sh or dash. We don't care about 10 - 20 ms, and jumping between shells isn't also beneficial.
Main: the content of setup-env-test.sh is distributed everywhere. Functions section_{start,end,switch}
and error
are available everywhere (GitLab, barebone, LAVA.. etc.)
Failure samples: