Support dnf5 for qubes-download-dom0-update.sh

[alimirjamali]

dnf5 does not print "--downloadonly" help with -h by default

For https://github.com/QubesOS/qubes-issues/issues/9244

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.14%. Comparing base (5b860df) to head (edae40c). Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #521      +/-   ##
==========================================
- Coverage   70.57%   70.14%   -0.43%     
==========================================
  Files           3        3              
  Lines         469      469              
==========================================
- Hits          331      329       -2     
- Misses        138      140       +2     

Flag	Coverage Δ
	70.14% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[alimirjamali]

Using --version to detect dnf5 in Debian scenario

[alimirjamali]

Reason for amendments:

In dnf5:

1. check-update is renamed to check-upgrade
2. The order of command & argument does matter very much.

[alimirjamali]

PipelineRetry