Refactor social network data load script to use just 20 queries

[alexjpwalker]

Product change and motivation

The social-network sample dataset now loads its data using very few queries (20, down from about 4800).

This allows HTTP-based clients to load it very quickly without getting bottlenecked hard by network latency.

Implementation

By making the match stages much chunkier we can drastically cut down on the total number of insert stages required to insert all data. For some types, we go from N queries to 1 for insertion of all instances of said type.

Note that due to a quirk of TypeDB server at the time of writing the chunky match stages are themselves chunked into pipelines that look like match-match-match .... match-insert, sometimes with as many as 100 match stages. This drastically improves performance.