refactor: use sudo softwareupdate --install --all --restart to update macOS

[SteveLauC]

use sudo softwareupdate --install --all --restart to update macOS

for more info, see the discussion in #546

Standards checklist:

• The PR title is descriptive.
• I have read CONTRIBUTING.md
• The code compiles (cargo build)
• The code passes rustfmt (cargo fmt)
• The code passes clippy (cargo clippy)
• The code passes tests (cargo test)
• Optional: I have tested the code myself

For new steps

• Optional: Topgrade skips this step where needed
• Optional: The --dry-run option works with this step
• Optional: The --yes option works with this step if it is supported by
  the underlying command

If you developed a feature or a bug fix for someone else and you do not have the
means to test it, please tag this person here.

[SteveLauC]

cc @DucretJe @reini-1, I don't have a macOS machine at hand so I cannot give you guys a binary to test, I am sorry.

[schrobingus]

I can test :^)

[SteveLauC]

I can test :^)

Thanks for your interest in helping with this issue, but it is indeed not that easy to solve this issue, see this comment

[pan93412]

I'd rather not restart here as there might be some cleanup needed before letting softwareupdate restart this device. However, the original command seems to restart even without the --restart flag. Can someone assist in testing these commands? :)