[ResponseOps][MW] Auto delete archived MWs

[cnasikas]

Maintenance windows can be archived from the UI but they are not deleted. We should use the task manager and delete archived MWs periodically. The docs also state Archived: It is archived. In a future release, archived maintenance windows will be queued for deletion.

DoD

• Create a task, using the task manager, that will run once per day and delete any archived MWs.
• The task should be of low priority and should not affect the rule execution.
• The task should delete the MWs in bulk and not all at once to avoid performance issues.
• The task should use the internal user to delete the MWs.
• Update the docs to state that the archived MWs are deleted periodically.

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)