Add command for "list-outdated"

[isc-shuliu]

Implement an outdated command mentioned in #427

[isc-kiyer]

@isc-shuliu this PR is related to #550 where part of running "update" should upgrade a module and run its upgrade steps (if any).

[isc-shuliu]

@isc-shuliu this PR is related to #550 where part of running "update" should upgrade a module and run its upgrade steps (if any).

Thanks for the heads-up! I'm aware of that hence posting it as a draft.

[isc-kiyer]

@isc-shuliu Doesn't look like this method is used?

[isc-shuliu]

Yes, you're right. I haven't gone to that point yet. My plan is to show if an outdated package can be updated to a particular version without violating dependency constraint. This PR is still a Work-In-Progress

[AshokThangavel]

Hi @isc-shuliu and @isc-kiyer
would like to check on the status of this PR. The list-outdated command would be a very valuable addition to the workflow. Is this still considered work-in-progress.
Also, if it helps move things forward, would you be open to integrating this logic into the existing list-installed command instead (perhaps via an --outdated or -o flag)? I’d be happy to implement it if that's a direction you'd like to take.
Thank you!