Fix samples tests for Java 10Illegal access warnings get grouped, causing extra lines in theactual samples output. Furthermore, play component report was notproperly normalized. This change adds normalization for the Javaversion string.
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+.