codeintel: Gob serialization
Created by: efritz
Replace JSON serialization format with gob. This simplifies the (working) code, although we need to keep the old code around for migrations (at least for a bit). This does does not affect read or write times, and does shave some additional space off of the existing databases (around ~10% with the sample databases I've tested with). The big benefit here, though, is code cleanliness.
In a future PR I'll deconstruct the old JSON serializer into the migrations that need to maintain that logic.