ci(java): introduce spotless-maven-plugin

[yanghua]

No description provided.

[yanghua]

In Java CI, when running mvn clean install, it will automatically invoke spotless-check phase.

If there is any code style issue, it will break the mvn command. The CI will fail.

Users or developers can use mvn spotless:apply to format code automatically based on Google Java Code style with a unified Spec.

In addition, we could also introduce git pre-commit-hook to make developers run this command before submitting a PR.

I believe, by introducing this plugin, the community will have a pleasing codebase. However, yes, it's unfortunate we need a one-shot reformat to initialize it.

cc @LuQQiu , FYI: Apache Iceberg, Flink, Kyuubi, and Hudi have all adopted this plugin.

[wjones127]

This seems reasonable to me 👍