Google Ads API Client Library for Java - v16.0.3

• Fix #543 to correctly classify the google-cloud-shared-dependencies dependency.
• Split project into multiple sub-modules to improve build times and separate
  generated code from core library code. No changes are required for projects
  with a dependency on the google-ads artifact.
• Customize the client used to upload artifacts to Sonatype Nexus during library releases (#544).

See change log for details.