Once the optimizer starts generating physical plans which perform shard filtering, we will need to update the lowering code to generate the corresponding SBE plan.

The ABT representation is an n-ary FunctionCall, with each parameter corresponding to a Variable representing a field of the shard key. The SBE representation is a 2-arg function with the first parameter pointer to a slot in the runtime environment representing the ShardFilterer and the second parameter being an expression evaluating to a BSONObj representing the shard key.