Support deb-get

[r-darwish]

Fixes #923

Standards checklist:

• The PR title is descriptive.
• 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
  • I also tested that Topgrade skips the step where needed

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.

[r-darwish]

@Zahrun please test this change

[Zahrun]

Thank you for the quick addition.
It seems the "update" step is not required since the only difference is that it will do "apt-get update", and we already do this in a previous topgrade step . So "upgrade" alone will work for deb-get.
Also we are missing this header:
―― 10:40:35 - deb-get ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

EDIT: you corrected the title before I posted. Let me test it.

[Zahrun]

The separator displays correctly.
We can remove the ctx.execute_elevated(&deb_get, false)?.arg("update").check_run()?; line and we are good.