chore: ignore aws-cdk-lib tests in npm package (#25086)

Add tests directories to .npmignore in aws-cdk-lib to decrease package size.

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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: MrArnoldPalmer

packages/aws-cdk-lib/.npmignore

@@ -5,6 +5,7 @@
 !*.d.ts
 !*.js
 test/
+**/test/**
 
 # Coverage
 coverage