Enable $lookup feature flag in all feature flag variants

Additionally do the following.

• In the SBE $lookup, we don't do replanning for the foreign-side per each local document. So the foreign collection profiling count is not increased by the number of local collection documents. Tests at profile_lookup.js needs to be updated for the SBE $lookup
• Do not run lookup_query_stats.js for the SBE $lookup feature until we implement proper query stats test cases for the SBE $lookup feature.