Provide an API to handle installation/restore of specific workloads by other extensions

[baronfel]

We should provide an API by which client extensions can request that certain .NET SDK workloads be installed, ideally with minimum baseline versions required by the tooling. This will allow for tooling experience to have a unified way of managing workload requirements and remove the need for separate extensions (Aspire, MAUI, etc) to re-implement this functionality.