[reconfigurator] BlueprintBuilder API allows non-planner clients to emit invalid blueprints

[jgallagher]

This is strongly related to #7078 and #7079. BlueprintBuilder exposes two methods that clients must call at appropriate times to emit blueprints with correctly-populated blueprint_datasets and blueprint_disks: sled_ensure_disks() and sled_ensure_datasets(). The planner calls these methods appropriately, so the production code path is correct, but we have many tests and reconfigurator-cli which use BlueprintBuilder directly without going through the planner that fail to call these methods, and therefore (can or do, depending on the test) emit blueprints with incorrect contents for those maps.

[davepacheco]

Is this the same as #6990? Was this also resolved by #7105?

[jgallagher]

Yeah I think so, thanks.