Add Automatic-Module-Name to JAR MANIFEST.MF

[saturnism]

Configure JAR plugin to add Automatic-Module-Name for our JAR distributions. Each artifact should have its own module name.

[anthmgoogle]

This seems like a repo-wide infrastructure question. @saturnism @lesv @garrettjonesgoogle can you determine feasibility of this suggestion, and if feasible we can turn this into a feature request or cleanup item.

[lesv]

This is a Java 9 FR. It's a common request: grpc/grpc-java#3523, grpc/grpc-java#3522, square/ok-http#3655

It should be trivial to do, see google/guava@f2be0be#diff-e407b6f223ee6c04116a91ead9f5e100R42 for an example.

[yihanzhen]

Move this issue to feature request backlog and close it here. This place can still be used for discussion.