Remove checked in generated code

[pkwarren]

Update codegen to generate to the build directory to minimize the code in this project and match other protovalidate projects.

Upgrade to Gradle 8.13.

[timostamm]

IMO generating to the build directory works well for java (and dotnet).
Where else do we do this? C++?

[smaye81]

Nice. Ran this locally and confirmed make works for me.

[pkwarren]

IMO generating to the build directory works well for java (and dotnet). Where else do we do this? C++?

Looks like C++ does. I think for Java this makes the most sense. I'd like to get protobuf upgrades fully automated via dependabot where we can ensure when protobuf-java is upgraded that we also regenerate code on the latest version. Right now that is a manual step:

protovalidate-java/gradle/libs.versions.toml

Lines 8 to 12 in 68daeff

	# When updating, make sure to update versions in the following files to match and regenerate code with 'make generate'.
	# - buf.gen.yaml
	# - conformance/buf.gen.yaml
	# - src/test/resources/proto/buf.gen.imports.yaml
	# - src/test/resources/proto/buf.gen.noimports.yaml