feat: add support for listing all sub-commands of a command

[remyleone]

Community Note

• Please vote on this pull request by adding a 👍 reaction to the original pull request comment to help the community and maintainers prioritize this request.
• Please do not leave "+1" or other comments that do not add relevant new information or questions, they generate extra noise for pull request followers and do not help prioritize the request

Relates OR Closes #0000

Release note for CHANGELOG:

[Copilot]

Pull request overview

This pull request adds a new --list-sub-commands flag to all commands in the Scaleway CLI, enabling users to list all available subcommands for any given command.

Changes:

• Added --list-sub-commands flag to the FLAGS section of all command usage outputs
• Updated test golden files to reflect the new flag in command help text

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.88%. Comparing base (e0a918f) to head (cae1e21).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5289      +/-   ##
==========================================
- Coverage   55.90%   55.88%   -0.02%     
==========================================
  Files         316      316              
  Lines       71606    71631      +25     
==========================================
+ Hits        40029    40032       +3     
- Misses      30084    30104      +20     
- Partials     1493     1495       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.