[8.16] Manual rule run docs

[nastasha-solomon]

Contributes to #5264

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• Manage detection rules | Run rules manually: New section
• Made the following changes to the "Monitor and troubleshoot rule executions" page:
  • Execution results: Updated intro and added new list items to describe the new filter and toggle added to the Execution log table.
  • Added a new section to explain the new Manual runs table.
• Bulk action API doc updates:
  • Request body - Made two changes:
    • Added the run value to the list of possible values for the action param.
    • Doc'd a new param named run
  • BulkManualRuleRun object - New section that shows how to edit the BulkManualRuleRun[] object.
  • BulkEditAction object | Response payload - Updated the list of actions that can be included in the response payload and refreshed the description for the attributes.results.updated field.
• Alert schema - Added a description for the new kibana.alert.intended_timestamp alert field.

Corresponding Serverless PR: #5589

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