Ship a first-class module-info.java

The module descriptor already exists but lives in the java9 multi-release tree and is compiled in a separate execution.

• Move module-info.java to src/main/java and compile it with the rest of the sources.
• Re-check exports, uses and provides against the public API, and keep optional dependencies (slf4j, AWS SDK) as requires static.
• Add a test that runs the driver on the module path (--module-path) with jlink, and a test that runs it on the class path, so both remain supported.
• Update the OSGi bnd.bnd exports to match.