[reconfigurator] Builder API does not provide guarantees that datasets are provisioned for zones, but should

[smklein]

Today, if you use the planner to provision a new zone, it'll provision a new zone in the constructed blueprint, and then invoke sled_ensure_datasets, which will create necessary records for that zone to exist.

However, if you use the reconfigurator-cli to provision a new zone, it'll make a new zone in the blueprint, but it will be missing a corresponding dataset (see also: #6987 , where we could catch this!). I believe our live-tests are also suffering from the same defect.

This issue tracks two things:

• We should patch these callsites, where zones are provisioned without datasets, to ensure that datasets are actually getting provisioned
• We should update the API to the builder to make it harder to misuse - provisioning a new zone should likely immediately provision a corresponding dataset (or datasets).

FYI @jgallagher

[jgallagher]

Fixed by #7105