Implement granular read_admin_monitoring permission

Background

• Add read support for granular permissions in the admin area for monitoring data
• Views
  • /system_info
  • /background_migrations
  • /health_check
  • /audit_logs
  • /gitaly

Documentation

• Permission Title: "View system monitoring"
• Permission name: `read_admin_monitoring`
• Permission Description: "Allows read access to system monitoring including system info, background migrations, health checks, audit logs, and gitaly in the Admin Area."
• Update prerequisites for feature documentation. Include links to feature pages.