Unique names for CDK test parameters and secrets

[fedonev]

Add an option to append a unique identifier to AWS physical resource names.

Hardcoded parameter and secret names now cause resource collisions if the CDK test app is deployed more than once in an environment.
Multiple deploys would make parallel integration testing easier.

dummy-string-secret -> dummy-string-secret-8e3ac2

Add an optional Stack prop? That would let test callers determine whether a unique id is required or not.

We cannot simply use generated resource names. The local test cases depend on fixed naming in the test output.