Epic: Support optional SDK workload composition

[dsplaisted]

Workloads overview spec

This Epic tracks the work needed for workload "composition", ie hooking up the right assets from a workload once they are installed.

This spec covers a lot of the details for how this will be implemented: Workload resolution in MSBuild

• Add features to MSBuild SDK Resolver interface to support optional SDK workloads
• Write library for reading workload manifests
• Create MSBuild SDK resolver for workloads
• Support workloads in Microsoft.NET.Sdk
• Workload library pack
• Template Engine - Workload work with template

.NET 6

• Project system - Trigger in-product acquisition based on MissingWorkloadPack items
• Create validator for workloads to make sure that they follow the right format and guidance
• Workload commandline resolver

[wli3]

We also need to have a new CLI command resolver to find the tools from a workload