Pre/post (aka non-exclusive) actions should be able to end execution

[KathleenDollard]

Pre (and later post) actions – called non-exclusive actions in the current PR – should be able to cancel. It will be awkward if they need to do something – like check a license – and then have to do something weird to ensure the CliAction does not proceed.

[adamsitnik]

Pre (and later post) actions – called non-exclusive actions in the current PR – should be able to cancel.

They can already do that:

override Task<int> InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken = default)
{
    return Task.FromCanceled(cancellationToken);
}