NIFI-16252 Add Reproducible Build workflow

[exceptionfactory]

Summary

NIFI-16252 Adds a reproducible-build GitHub workflow that uses the Maven Artifact Compare plugin goal to evaluate binary hashes of build packages.

The workflow performs a Maven install build with the apache-release profile activated to align with release build processes. After the reference build, the artifact:compare goal runs a subsequent build to compare original artifact hashes with repeated build hashes.

The workflow is scheduled to run on pull requests as an independent workflow. Initial runs on a project fork show successful status for all artifacts, taking around 45 minutes. This amount of time aligns with or falls under the existing build workflow, so it will not block completion of workflow evaluation.

Tracking

Please complete the following tracking steps prior to pull request creation.

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number, such as NIFI-00000
• Pull Request commit message starts with Apache NiFi Jira issue number, as such NIFI-00000
• Pull request contains commits signed with a registered key indicating Verified status

Pull Request Formatting

• Pull Request based on current revision of the main branch
• Pull Request refers to a feature branch with one commit containing changes

Verification

Please indicate the verification steps performed prior to pull request creation.

Build

• Build completed using ./mvnw clean install -P contrib-check
  • JDK 21
  • JDK 25

Licensing

• New dependencies are compatible with the Apache License 2.0 according to the License Policy
• New dependencies are documented in applicable LICENSE and NOTICE files

Documentation

• Documentation formatting appears as expected in rendered files

[pvillard31]

Thanks @exceptionfactory - this LGTM