Uses CustomEvents within ImportJobs

[andyHa]

Description

Makes import jobs dispatch custom events.

Example Scripts:

registry.registerHandler(sirius.biz.jobs.batch.ImportJobStartedEvent.class,  |e| log(e));

registry.registerTypedHandler(sirius.biz.importer.BeforeFindEvent.class, MongoUserAccount.class, |e| log(e));

registry.registerTypedHandler(sirius.biz.importer.OnLoadEvent.class, MongoUserAccount.class, |e| log(e));

registry.registerTypedHandler(sirius.biz.importer.BeforeCreateOrUpdateEntityEvent.class, MongoUserAccount.class, |e| log(e));

Relates to:

• Provides some groundwork for script based import customizations. #1959
• Provides a main framework for custom scripting #1960
• Uses CustomEvents within ImportJobs #1961

Checklist

• Code change has been tested and works locally
• Code was formatted via IntelliJ and follows SonarLint & best practices
• Patch Tasks: Is local execution of Patch Tasks necessary? If so, please also mark the PR with the tag.