feat: added template for java binary builder

[rohansen856]

Summary

This PR introduces a JavaBinaryBuilder plugin following the same patterns and lifecycle as the existing GoBinaryBuilder.
The goal is to support Java repositories by producing a versioned .jar artifact that can be uploaded to GitHub Releases in a consistent way.

Currently implemented things

• Auto-detect build system: Maven (pom.xml) or Gradle (build.gradle / build.gradle.kts)

• JAR is the standard packaged output for Java projects and is the closest equivalent “release artifact” for this builder system, so the “binary” for Java is treated as a JAR (not a native ELF executable).

• Builds are executed inside Docker containers using the repo mounted into /app, as it ensures reproducible builds across dev machines + CI environments and follows the same execution model as the Go builder.

• the default Docker image is Maven + Temurin JDK 17 as Java 17 is a stable LTS choice and Maven is common. see: https://hub.docker.com/layers/library/maven/3.9-eclipse-temurin-17/images/sha256-078164c49b664077cd330ad6cd367eb3baa5188380d68c82bf364c04c11748e9

Questions before i finalize the PR

• What should "Java binary" mean for this system... plain jar or fat/uber jar
• when multiple jars exist, should we prioritize shaded jars / Spring Boot jars?

So, Once the above decisions are confirmed, I will update the builder into a finalized implementation and push the changes.
PS, I havent yet manually tested this on a java project, but will do thst once the code is ready.

cc @pleia2 @rposts