devenv: make common CLI options global

[sandydoo]

Before

➜ devenv shell --help
Activate the developer environment. https://devenv.sh/basics/

Usage: devenv shell [CMD] [ARGS]...

Arguments:
  [CMD]
  [ARGS]...

Options:
  -h, --help  Print help

After

➜ devenv shell --help
Activate the developer environment. https://devenv.sh/basics/

Usage: devenv shell [OPTIONS] [CMD] [ARGS]...

Arguments:
  [CMD]
  [ARGS]...

Options:
  -v, --verbose
          Enable debug log level.
  -j, --max-jobs <MAX_JOBS>
          Maximum number of Nix builds at any time. [default: 4]
  -s, --system <SYSTEM>
          [default: aarch64-linux]
  -i, --impure
          Relax the hermeticity of the environment.
      --offline
          Disable substituters and consider all previously downloaded files up-to-date.
  -c, --clean [<CLEAN>...]
          Ignore existing environment variables when entering the shell. Pass a list of comma-separated environment variables to let through.
  -d, --nix-debugger
          Enter Nix debugger on failure.
  -n, --nix-option <NIX_OPTION> <NIX_OPTION>
          Pass additional options to nix commands, see `man nix.conf` for full list.
  -o, --override-input <OVERRIDE_INPUT> <OVERRIDE_INPUT>
          Override inputs in devenv.yaml.
  -h, --help
          Print help