NOTE: This is no longer the plan for supporting spilling to disk when sorting for calculating accurate percentiles. See SERVER-92993 and SERVER-92994 for the current plan. This ticket is being kept as a record in case some of the logic developed is needed for the new implementation.

We'll use a sortExecutor to implement the algorithm described in the design document. The same algorithm will be used for both continuous and discrete, replacing the current implementation for the latter.