Version task-manager task state

[kobelb]

Feature Description

To enable zero downtime upgrades, we need to version the task manager's task state. This will allow us to ensure that if an older Kibana node runs an alerting rule after a newer Kibana node has stored additional task state, the unknown state properties will be dropped. Additionally, this will prompt developers to be aware that adding required fields to the task state is a breaking change that must be handled with care.

Business Value

Facilitates zero downtime rolling upgrades and rollbacks, allowing us to roll-out new features to our users more quickly while they continue to use the system without disruption.

Definition of Done

• Task Manager consumers can declare multiple versions for the task state
• Unit tests passed

[elasticmachine]

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

[mikecote]

Implementation of this capability will be done in the following steps. Adding Meta label:

• https://github.com/elastic/kibana/pull/159048
• https://github.com/elastic/kibana/issues/159342
• https://github.com/elastic/kibana/issues/159343
• https://github.com/elastic/kibana/issues/159344
• https://github.com/elastic/kibana/issues/159345
• https://github.com/elastic/kibana/issues/159346
• https://github.com/elastic/kibana/issues/159347
• https://github.com/elastic/kibana/issues/159964