.NET: [Feature Branch] Add Human In the Loop support for durable workflows (#4358)

* Add Azure Functions HITL workflow sample

Add 06_WorkflowHITL Azure Functions sample demonstrating Human-in-the-Loop
workflow support with HTTP endpoints for status checking and approval responses.

The sample includes:
- ExpenseReimbursement workflow with RequestPort for manager approval
- Custom HTTP endpoint to check workflow status and pending approvals
- Custom HTTP endpoint to send approval responses via RaiseEventAsync
- demo.http file with step-by-step interaction examples

* PR feedback fixes

* Minor comment cleanup

* Minor comment clReverted the `!context.IsReplaying` guards on `PendingEvents.Add`/`RemoveAll` and `SetCustomStatus` in `ExecuteRequestPortAsync`. The guards broke fan-out scenarios where parallel RequestPorts      need to be discoverable after replay. `SetCustomStatus` is idempotent metadata that doesn't affect replay determinism.eanup

* fix  for PR feedback

* PR feedback updates

* Improvements to samples

* Improvements to README

* Update samples to use parallel request ports.

* Unit tests

* Introduce local variables to improve readability of Workflows.Workflows access patter

* Use GitHub-style callouts and add PowerShell command variants in HITL sample README

dotnet/src/Microsoft.Agents.AI.DurableTask/DurableOptions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System.Diagnostics;
 using Microsoft.Agents.AI.DurableTask.Workflows;
@@ -9,7 +9,7 @@ namespace Microsoft.Agents.AI.DurableTask;
 /// Provides configuration options for durable agents and workflows.
 /// </summary>
 [DebuggerDisplay("Workflows = {Workflows.Workflows.Count}, Agents = {Agents.AgentCount}")]
-public sealed class DurableOptions
+public class DurableOptions
 {
     /// <summary>
     /// Initializes a new instance of the <see cref="DurableOptions"/> class.