feat(core): add creation policy configuration for appstream (#23607)

Fixes #23604 

I have:
- added startFleet to CfnCreationPolicy, including doc remarks for the property and the class.
- added a unit test to test wether it is rendered correctly in the CloudFormation template.
- added and ran an intergrity test in aws-appstream to verify that the Fleet is actually started.

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### Adding new Construct Runtime Dependencies:

* [ ] This PR adds new construct runtime dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md/#adding-construct-runtime-dependencies)

### New Features

* [x] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [x] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: Jacco

Diff for: packages/@aws-cdk/aws-appstream/package.json

@@ -83,6 +83,8 @@
   "devDependencies": {
     "@aws-cdk/assertions": "0.0.0",
     "@aws-cdk/cdk-build-tools": "0.0.0",
+    "@aws-cdk/integ-runner": "0.0.0",
+    "@aws-cdk/integ-tests": "0.0.0",
     "@aws-cdk/cfn2ts": "0.0.0",
     "@aws-cdk/pkglint": "0.0.0",
     "@types/jest": "^27.5.2"