Enforce timeout for tests not marked as Slow

[ScottDugas]

Right now the build doesn't generally enforce the time that a test takes, so if someone tries to run skipping Slow tests it can actually take a long time. We should change the test framework to enforce the time.

We can do this by replacing our current:

@Tag(Tags.Slow)

With an annotation which will bring with it an elevated timeout, and then set a smaller default timeout. e.g.:

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Timeout(value = 5, unit = TimeUnit.MINUTES)
@Tag(Tags.Slow)
public @interface SlowTest {
}