Enable opt out of V3 language worker breaking changes in host.json

If we allow for users to opt out of specific breaking changes for V3, we should not do this using the App Setting for feature flags. This information should be contained in host.json so that a deployed payload will always have consistent behavior with the local payload.

cc: @fabiocav and @brettsam and @jeffhollan

Start with the host.json configuration path named in the issue and determine which V3 language-worker breaking changes need individual opt-outs. Clarify the host.json schema and the expected behavior for deployed versus local payloads; done means the selected opt-outs are persisted with the payload rather than supplied through App Settings.

Written by the indexing model from the issue text.