Provide an Automatic-Module-Name

**Is your feature request related to a problem? Please describe.**
It is currently not possible to create modular applications which depend on `google-cloud-kms` it is not module-ready.

**Describe the solution you'd like**
Define an `Automatic-Module-Name` in `MANIFEST.MF` to make `google-cloud-kms` module-ready.

**Describe alternatives you've considered**
The only alternatives are giving up creating modular applications or repackaging `google-cloud-kms` to add the required metadata.

**Additional context**
Providing `Automatic-Module-Name` has no impact on non-modular applications or applications targeting Java 8.