.NET: [BREAKING] Workflows API Review Naming Changes (Part 1?) (#4090)

* refactor: Normalize Run/RunStreaming with AIAgent

* refactor: Clarify Session vs. Run -level concepts

* Rename RunId to SessionId to better match Run/Session terminology in AIAgent
* [BREAKING]: Will break existing checkpointed sessions in CosmosDb due to field rename

* refactor: Rename and simplify interface around getting typed data out of ExternalRequest/Response

* Also adds hints around using value types in PortableValue

* refactor: Rename AddFanInEdge to AddFanInBarrierEdge

This will prevent a breaking change later when we introduce a programmable FanIn edge, analogous to the FanOut edge's EdgeSelector.

The goal, in the long run is to support a number of different FanIn scenarios, with naive FanIn (no barrier) by default, similar to FanOut.

* refactor: AsAgent(this Workflow, ...) => AsAIAgent(...)

* misc - part1: SwitchBuilder internal

---------

Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>

dotnet/src/Microsoft.Agents.AI.Workflows/ConfigurationExtensions.cs

@@ -16,7 +16,7 @@ public static class ConfigurationExtensions
     /// <param name="configured">The existing configuration for the subject type to be upcast to its parent type. Cannot be null.</param>
     /// <returns>A new <see cref="Configured{TParent}"/> instance that applies the original configuration logic to the parent type.</returns>
     public static Configured<TParent> Super<TSubject, TParent>(this Configured<TSubject> configured) where TSubject : TParent
-        => new(async (config, runId) => await configured.FactoryAsync(config, runId).ConfigureAwait(false), configured.Id, configured.Raw);
+        => new(async (config, sessionId) => await configured.FactoryAsync(config, sessionId).ConfigureAwait(false), configured.Id, configured.Raw);
 
     /// <summary>
     /// Creates a new configuration that treats the subject as its base type, allowing configuration to be applied at