Support format expressions for routing in the opensearch sink

[graytaylor0]

Is your feature request related to a problem? Please describe.
As a user of the opensearch sink and the routing_field, I would like to dynamically format my _routing id using one or more metadata keys or keys in the Event

Describe the solution you'd like
A new routing_id parameter that supports format expressions. This would follow a similar path of the movement from document_id_field to document_id,

Describe alternatives you've considered (Optional)
Configuring extra add_entries processors to create format expressions in the actual Event, and then using exclude_keys in the sink to remove the custom routing field.

Additional context
Add any other context or screenshots about the feature request here.