chore: record cdk8s usage in stack metadata (#24849)

Adding `cdk8s.` to the list of packages we record metadata for.

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

Author: iliapolo

packages/@aws-cdk/core/lib/private/runtime-info.ts

@@ -7,7 +7,7 @@ const ALLOWED_FQN_PREFIXES = [
   // SCOPES
   '@aws-cdk/', '@aws-cdk-containers/', '@aws-solutions-konstruk/', '@aws-solutions-constructs/', '@amzn/', '@cdklabs/',
   // PACKAGES
-  'aws-rfdk.', 'aws-cdk-lib.',
+  'aws-rfdk.', 'aws-cdk-lib.', 'cdk8s.',
 ];
 
 /**