Allow stack updates to be cancelled in CloudFormation delete (and maybe elsewhere)

**Is your feature request related to a problem? Please describe.**
AWS ECS takes three hours to timeout if there's an issue during a stack update

**Describe the solution you'd like**
Allow stack updates to be cancelled, like with the [CancelUpdateStack API](https://docs.aws.amazon.com/AWSCloudFormation/latest/APIReference/API_CancelUpdateStack.html)

**Describe alternatives you've considered**
Use the `CloudFormationDeleteStack` task to cancel the stack update. This used to work before, but now it displays the following error:
> ##[error]ValidationError: Stack cannot be deleted while in status UPDATE_IN_PROGRESS

Start by locating the CloudFormationDeleteStack task and the stack-operation entry points, then compare their behavior with the AWS CancelUpdateStack API named in the issue. Done means an in-progress stack update can be cancelled instead of failing with the reported UPDATE_IN_PROGRESS deletion error; the issue does not name specific files or tests.

Written by the indexing model from the issue text.