Motivation for this change

Lay the groundwork for azure-cli repo, which is the "new azure cli standard". Also know as "azure cli 2.0".

The azure-cli package will have to wait for #60435 to be merged. And then nix will have modern support for azure :) (at least cli, nixops will be later)

Separate from #60435

Works with python2, python3.6 and python3.7. Unfortunately contextvars is needed for one of the dependencies (msrest) so it's broken on python3.5.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

$ nix path-info -Sh /nix/store/fsdvfxzz6bwgdvzdhnziw5rjnpjjr896-python3.6-azure-cli-core-2.0.66
/nix/store/fsdvfxzz6bwgdvzdhnziw5rjnpjjr896-python3.6-azure-cli-core-2.0.66 135.5M