Externalize samples testing infrastructureThis change replaces UserGuideSamplesRunner with an external librarycalled sample-check. Sample discovery, execution, and normalizationis delegated to this library, with some custom normalizers remainingin the Gradle codebase.Samples output has become co-located with the sample code. Samples testsmust be run with Java 8+.
Changed the documentation (samples) to improve testability. In ant samples I stopped using ant.checksum task that potentially gave different results based on environment (due to line endings, etc.). Instead, I started using ant.loadfile task.