Restructure CI pipeline configuration

[terhorstd]

Update Github workflow with the following modifications

• separate static code checks from build jobs
• fix dependency management (a bit) due to wrongly interpreted syntax
• add set -euo pipefail to CI scripts to catch false negatives.
• register output logs as artifacts (visible on actions page)

Some preparatory modifications of the build scripts, notably:

• sorting of files in extras/ to more meaningful locations:
  • created bin/
  • rename of many files {extras,build_support}/*
• many cleanups of spurious whitespaces and unhandled (and unseen) undefined variables and conditions

Started cleaning up dependency management

• renamed conda environment files to standard names
• adapted documentation to new dependency handling

[jougs]

Thanks for this extensive cleanup. I've left some inline comments, but am mostly fine as is.

[jougs]

LGTM! Thanks again for this massive cleanup :-)

[pnbabu]

@terhorstd I just have this small comment on your reply. Can you please have a look?

[jougs]

@pnbabu: could you please resolve the open discussions and indicate if you request further changes?
@terhorstd: could you please resolve the conflict that popped up?

Thanks!