Upgrade of .NET agent for Azure Pipelines

This post announces the upgrade of the Azure Pipelines agent from .NET Core 3.1 to .NET 6, driven by the need to support new hardware like Apple Silicon and newer operating systems. It explicitly lists operating systems that will no longer be supported by the .NET 6 agent, outlines a phased rollout plan (Preview, GA for Microsoft-hosted, GA for self-hosted), and provides mitigation strategies for users on unsupported OSes, including a script to identify incompatible agents and warnings for pipeline runs. It also clarifies the distinction between 2.x (.NET Core 3.1) and 3.x (.NET 6) agents and discusses security patching and future feature requirements.