Add a new method to the SA's gRPC interface which takes both an Order
and a list of new Authorizations to insert into the database, and adds
both (as well as the various ancillary rows) inside a transaction.
To enable this, add a new abstraction layer inside the `db/` package
that facilitates inserting many rows at once, as we do for the `authz2`,
`orderToAuthz2`, and `requestedNames` tables in this operation.
Finally, add a new codepath to the RA (and a feature flag to control it)
which uses this new SA method instead of separately calling the
`NewAuthorization` method multiple times. Enable this feature flag in
the config-next integration tests.
This should reduce the failure rate of the new-order flow by reducing
the number of database operations by coalescing multiple inserts into a
single multi-row insert. It should also reduce the incidence of new
authorizations being created in the database but then never exposed to
the subscriber because of a failure later in the new-order flow, both by
reducing failures overall and by adding those authorizations in a
transaction which will be rolled back if there is a later failure.
Fixes#5577
Aaron Gable