[sdk-platform-java] [GraalVM] Include missing grpc configurations for Direct Path support

This was discovered during an offline discussion with @BenWhitehead on https://github.com/googleapis/java-storage/issues/2716 where Storage ran into a run-time failures in graalvm when adding Direct Path support.

The solution (in progress) has been to include reflection configurations for `io.grpc` classes (https://github.com/googleapis/java-storage/issues/2716).

In the future, we should consider hosting or generating these generic configurations in `sdk-platform-java` to avoid duplicating this effort for libraries considering adding direct path support in the future.

cc/ @burkedavison