(core) Add support for Stack Policies

## :question: General Issue

### The Question

I need help trying to find the [concepts][1] that exists in CloudFormation UpdateStack wherein you can specify an 'StackPolicy' or 'StackPolicyDuringUpdate'. How does one achieve the same or similar concepts in a CDK engineered solution?

I found concepts such as [DeletionPolicy and UpdateRetentionPolicy][2] and at first glance they seemed like they could be used, but they are not quite the same things. Or the documentation/implementations are not doing what a StackPolicy would do.

[1]: https://docs.aws.amazon.com/AWSCloudFormation/latest/APIReference/API_UpdateStack.html
[2]: https://docs.aws.amazon.com/cdk/api/latest/java/software/amazon/awscdk/core/RemovalPolicy.html

Start with the linked CloudFormation UpdateStack API reference and compare StackPolicy and StackPolicyDuringUpdate with the linked CDK RemovalPolicy documentation. Define the desired CDK representation and verify that it preserves the policy semantics during stack updates; the issue provides no repository file or test entry point.

Written by the indexing model from the issue text.