Sidekiq worker to delete self-monitoring project

What does this MR do?

Create a Sidekiq worker which executes the Gitlab::DatabaseImporters::SelfMonitoring::Project::DeleteService:

1. The worker has an .in_progress? class method that takes a job_id parameter and checks Sidekiq::Status to return true if the job is enqueued or in progress.

2. Move specs from spec/workers/self_monitoring_project_create_worker_spec.rb into shared_examples so that they can be used in spec/workers/self_monitoring_project_delete_worker_spec.rb.

Issue: #32351 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team