Add a way to cancel PlanPreview for pipedv1

[khanhtc1202]

What would you like to be added:

We can cancel deployment via the deployment page on the PipeCD console, but we don't have any way to cancel other kinds of commands to piped effectively. Up to now, mostly we can just wait for those commands to be marked as orphan or timeout, but in some cases, users may need a way to cancel those commands (planpreview command for example)

This issue is more like an open for discuss/opinions, and could be convert to discussion later.

Why is this needed:

[github-actions[bot]]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions[bot]]

This issue was closed because it has been stalled for 7 days with no activity. Feel free to reopen if still applicable.

[atpugtihsrah]

@khanhtc1202 I would like to contribute to this issue. Could you please assign this to me?

[khanhtc1202]

Great, thanks @atpugtihsrah I will assign this to you, thank you 🙏 Also, since this one is quite complex, please join the MTG so that we can discuss this more effectively.

[atpugtihsrah]

Thanks @khanhtc1202 I'll join the next MTG on 21.05 :)

[kirat10x]

@atpugtihsrah are u working upon this currently

[atpugtihsrah]

@kiratlog Yes I am working on this thats why its assigned to me

[atpugtihsrah]

Communicating that I am still working on this. Did not have too much time in the last few weeks but I am still on top of this.

[atpugtihsrah]

@khanhtc1202 As discussed in the community meeting, I changed the title to reflect that this cancel command is only for v1.