Currently optimizer_base depends on //src/mongo/db:sbe_values.
One of the dependencies is through explain.cpp which implements:

    static void planCacheEntryToBSON(const mongo::PlanCacheEntry& entry, BSONObjBuilder* out);
    static void planCacheEntryToBSON(const mongo::sbe::PlanCacheEntry& entry, BSONObjBuilder* out);

The second planCacheEntryToBSON uses mongo::sbe::PlanCacheEntry.

This ticket moves the implementation of these functions to their corresponding definitions of PlanCacheEntry either as separate methods or serialization functions for planCacheEntry. Once the move is complete, address the corresponding dependencies.