Adding local ToListAsync method in Copilot Chat (microsoft#1346)

### Motivation and Context
The `System.Linq.Async` package reference was removed from the core
libraries so that everyone using SK wasn't forced to use it as well.
This adds a helper `ToListAsync` method to enable async conversion of
`IAsyncEnumerable<T>` to `List<T>` object.

### Description
Was seeing the following error when using local project references, so
this is an effort to future proof any SK nuget updates

`'IAsyncEnumerable<MemoryQueryResult>' does not contain a definition for
'ToListAsync' and no accessible extension method 'ToListAsync' accepting
a first argument of type 'IAsyncEnumerable<MemoryQueryResult>' could be
found (are you missing a using directive or an assembly reference?) `

samples/apps/copilot-chat-app/webapi/CopilotChat/Controllers/BotController.cs

@@ -13,6 +13,7 @@
 using Microsoft.Extensions.Options;
 using Microsoft.SemanticKernel;
 using Microsoft.SemanticKernel.Memory;
+using SemanticKernel.Service.CopilotChat.Extensions;
 using SemanticKernel.Service.CopilotChat.Models;
 using SemanticKernel.Service.CopilotChat.Options;
 using SemanticKernel.Service.CopilotChat.Storage;

samples/apps/copilot-chat-app/webapi/CopilotChat/Extensions/IAsyncEnumerableExtensions.cs

@@ -0,0 +1,26 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace SemanticKernel.Service.CopilotChat.Extensions;
+
+/// <summary>
+/// Extension methods for enabling async LINQ operations on IAsyncEnumerable sequence.
+/// </summary>
+public static class IAsyncEnumerableExtensions
+{
+    /// <summary>
+    /// Creates a List<T> from an IAsyncEnumerable<T> by enumerating it asynchronously.
+    /// </summary>
+    internal static async Task<List<T>> ToListAsync<T>(this IAsyncEnumerable<T> source)
+    {
+        var result = new List<T>();
+        await foreach (var item in source.ConfigureAwait(false))
+        {
+            result.Add(item);
+        }
+
+        return result;
+    }
+}

samples/apps/copilot-chat-app/webapi/CopilotChat/Skills/ChatSkills/SemanticChatMemoryExtractor.cs

@@ -8,6 +8,7 @@
 using Microsoft.SemanticKernel;
 using Microsoft.SemanticKernel.AI.TextCompletion;
 using Microsoft.SemanticKernel.Orchestration;
+using SemanticKernel.Service.CopilotChat.Extensions;
 using SemanticKernel.Service.CopilotChat.Options;
 
 namespace SemanticKernel.Service.CopilotChat.Skills.ChatSkills;
@@ -129,7 +130,7 @@ internal static async Task CreateMemoryAsync(
                 minRelevanceScore: options.SemanticMemoryMinRelevance,
                 cancellationToken: context.CancellationToken
             )
-            .ToListAsync(context.CancellationToken)
+            .ToListAsync()
             .ConfigureAwait(false);
 
         if (memories.Count == 0)