Allow stack policies to be set with CloudFormation tasks

**Is your feature request related to a problem? Please describe.**
Accidental updates to stack resources can't be prevented with CloudFormation tasks

**Describe the solution you'd like**
Allow stack policies to be set with CloudFormation tasks

**Describe alternatives you've considered**

- The AWS CLI can be used to set the stack policy after the stack is created
- The AWS CLI can be used instead of the CloudFormation tasks

Start by locating the TypeScript implementation and tests for the CloudFormation tasks, then inspect how task inputs are defined and passed to AWS. Confirm the existing task flow before deciding where stack policy configuration belongs. Done means a CloudFormation task can set a stack policy and prevent the targeted accidental resource updates, with coverage for the new behavior.

Written by the indexing model from the issue text.