Remove current_user from JobsFinder

What does this MR do?

Removes the current_user constructor argument and all authentication logic from ::Ci::JobsFinder's constructor.

In all use cases of Ci::JobsFinder, the internal authentication duplicated existing authentication in controllers and API endpoints.

This MR is preliminary work needed to merge Security::JobsFinder into ::Ci::JobsFinder, which will allow all stages to fetch jobs filtered by report_type.

This is the first MR for #251015 (closed)

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.