Change all browser-side clients and UI to handle additive changes

[kobelb]

Feature Description

Additive changes can be made to internal HTTP APIs without creating a new major version. Additionally, old browser-side code will be able to run against newer server-side code, resulting in browser-side code needing to adapt to the additive changes made to these HTTP APIs. As a result, browser-side code will need to be updated to handle additive changes, primarily the addition of new response fields and new values added to non-inclusive enums.

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

• All browser-side code updated to handle unknown response fields
• All browser-side code updated to handle values added to non-exclusive enums
• Unit tests

[elasticmachine]

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