Add updating notes confidentiality to Service

What does this MR do?

It changes the Notes::UpdateService so that it updates notes confidentiality. If note confidentiality is changed and the note is the discussion root, the confidentiality of all responses is changed accordingly.

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.

Preparation for #207473 (closed) and #207472 (closed) udpates