Add Commenting to Read-Only Cases

[morgan-atwood]

Describe the feature: Enable commenting on cases without giving users the ability to edit the main content or change case status. This would allow users to participate by adding observations or updates, while keeping the case itself locked from edits. Describe a specific use case for the feature: This feature is particularly useful when clients require that only certain team members have the ability to manage cases. For example, a client might want junior analysts to add comments and observations to cases without the risk of them modifying any critical case information or settings.

[elasticmachine]

Pinging @elastic/response-ops-cases (Feature:Cases)

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[cnasikas]

cc @shanisagiv1 @heespi

[heespi]

Added to our next refinement sync for discussion on scope and prioritization. @cnasikas