Split the JUnit 5 `OutputCapture` class into separate `OutputExtension` and `CapturedOutput` classes. The JUnit 5 callback methods are now contained only in the `OutputExtension` class so no longer pollute the public API that users will interact with. The `CapturedOutput` class has also been updated to capture System.err and System.out separately to allow distinct assertions if required. Closes gh-17029
== Spring Boot Liquibase Sample This sample demonstrates the liquibase auto-configuration support. You can look at `http://localhost:8080/actuator/liquibase` to review the list of scripts. This sample also enables the H2 console (at `http://localhost:8080/h2-console`) so that you can review the state of the database (the default jdbc url is `jdbc:h2:mem:testdb`).