Java: Package GPU native libraries in Maven.

And update version to 1.5.0-rc0.
Starting with 1.5.0-rc0, it will be possible to use GPUs from TensorFlow Java
programs by adding the following to the application's pom.xml:

<dependency>
  <groupId>org.tensorflow</groupId>
  <artifactId>libtensorflow</artifactId>
  <version>1.5.0-rc0</version>
</dependency>
<dependency>
  <groupId>org.tensorflow</groupId>
  <artifactId>libtensorflow_jni_gpu</artifactId>
  <version>1.5.0-rc0</version>
</dependency>

Updates #12909

PiperOrigin-RevId: 180816468