Add an azd ai dataset extension for Foundry datasets

### What

`azd` has no way to create or version Foundry datasets. A dataset is uploaded by
hand against the data plane, so the evaluation that grades against it cannot be
described in the project at all.

### Proposal

Add an `azd ai dataset` extension that registers a dataset and publishes its
versions, so a dataset is declared alongside the rest of the project and
published by the same deploy that publishes everything else.

Companion to #9549, which adds the `azd ai eval` extension that consumes them.

Start by reading the existing azd ai command extensions and the companion issue #9549 to understand how Foundry evaluations are represented. The work is done when a dataset can be declared, registered, and have its versions published through the same deploy that publishes the rest of the project.

Written by the indexing model from the issue text.