NIFI-14859: Fix PMD warnings by adding @Override annotations

[lfrancke]

Summary

NIFI-14859: Fix PMD warnings by adding Override annotations
Also updates the PULL_REQUEST_TEMPLATE.md to use the Maven Wrapper

NIFI-14859

Tracking

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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 Formatting

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

Verification

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Build

• Build completed using mvn clean install -P contrib-check
  • JDK 21

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

[lfrancke]

The macos test failures are unrelated