[ResponseOps][MW] Maintenance window: The road to GA

[cnasikas]

Kibana alerting supports the creation of maintenance windows (MW). Users, with the use of MW, can reduce rule notifications. They can schedule single or recurring maintenance windows, use KQL to filter the alerts affected by the maintenance window, or select the categories of rule types the maintenance window will affect. The MW feature is in technical preview. Before we make it GA we need to rethink some of its functionalities, fix bugs, and do enhancements. This meta ticket serves as a list of all tasks that need to be done before making the MW GA.

[elasticmachine]

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