Automate protobuf generated test POJOs

[onobc]

The Protobuf POJOs used for testing recently got out of sync w/ reality and tests started failing due to:

java.lang.UnsupportedOperationException: As of 2022/09/29 (release 21.7) makeExtensionsImmutable should not be called from protobuf gencode. If you are seeing this message, your gencode is vulnerable to a denial of service attack. You should regenerate your code using protobuf 25.6 or later. Use the latest version that meets your needs. However, if you understand the risks and wish to continue with vulnerable gencode, you can set the system property -Dcom.google.protobuf.use_unsafe_pre22_gencode on the command line. See security vulnerability: GHSA-h4h5-3hr4-j3g2

Just needed to update the generated POJOs. However, we should automate the process to regeenerate the files when building using a plugin such as https://github.com/google/protobuf-gradle-plugin