[RUN4247] Enforce project-level authorization on execution metrics API

[ronaveva]

This pull request updates the API documentation to clarify the authorization requirements for accessing execution metrics. The new section explains in detail how access is determined based on the project and query parameters.

Documentation update:

• Added a section specifying that read access for the event resource type is required to obtain execution metrics, with clear rules for project-specific, job-filtered, and global queries, and how authorization affects the results and error responses.

OSS PR related: https://github.com/rundeck/rundeck/pull/10419

[Copilot]

Pull request overview

Updates the Rundeck API documentation to describe the project-scoped authorization rules enforced by the Execution Metrics endpoints, including how the project and jobIdListFilter inputs affect access and results.

Changes:

• Documented required read permission on the event resource type for execution metrics queries.
• Clarified authorization behavior for project-scoped, job-filtered, and global (no project) metrics queries, including when 403 responses occur.