NIFI-14996 Add default implementation for clear Bulletin methods

[exceptionfactory]

Summary

NIFI-14996 Adds a default implementation for the new clear Bulletin methods on the BulletinRepository interface to avoid breaking changes in the next minor release version of the NiFi API.

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 Formatting

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

[mcgilman]

Thanks for the PR @exceptionfactory!