Load schemas in parallel instead of one-by-one. Optimizes from 2m30s to 1m15s. Change-Id: I0bf6381a0ae99b44271fe55d4ee658683064c097
first, so that they all work the same way, because it's getting complicated, and second, so that we can do the appropriate thing instead of CREATE SCHEMA for cockroachdb. Change-Id: I27fbaeeb6223a3e06d97bcf692a2d014b31465f7