https://jira.mongodb.org/browse/SERVER-110273 Introduced the concept of DistributedPlanLogic to the Extensions API.

As part of this ticket:

1. Add the required function get_distributed_plan_logic to the LogicalStage's vtable.
2. Update the LogicalStage's adapters to accommodate the new function.
3. Modify any existing test extensions such that they implement the new function.
4. Implement a test extension which implements DPL, and must always run on the merge pipeline. This is key to ensuring that we meet the requirements for $rerank. 

Note:
When $rerank is run on a sharded cluster, the stage must always be run on the router/merging node. This is because we would like to perform the $rerank over the entire merged results as opposed to on each individual shard. 

Currently, there are no stageConstraints which allow specifying this behaviour. We considered adding new stage constraints or static properties to achieve this behaviour, but instead, we'll be relying on DPL semantics to achieve the same result.