.Net - Performance Fix for Orchestration Result (#13317)

### Motivation and Context
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Using synchronous `WaitAll` creates extra CPU load at scale.

### Description
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Use asynchronous `WhenAny` with timeout for modern .NET and using
`Delay` task for .netstandard.

### Contribution Checklist
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- [X] The code builds clean without any errors or warnings
- [X] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
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raises no violations
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- [ ] I didn't break anyone 😄

Author: crickman

dotnet/src/Agents/Orchestration/OrchestrationResult.cs

@@ -73,12 +73,24 @@ public async ValueTask<TValue> GetValueAsync(TimeSpan? timeout = null, Cancellat
 
         if (timeout.HasValue)
         {
-            Task[] tasks = { this._completion.Task };
-            if (!Task.WaitAll(tasks, timeout.Value))
+#if NET
+            try
+            {
+                await this._completion.Task.WaitAsync(timeout.Value, cancellationToken).ConfigureAwait(false);
+            }
+            catch (TimeoutException)
+            {
+                this._logger.LogOrchestrationResultTimeout(this.Orchestration, this.Topic);
+                throw;
+            }
+#else
+            Task completedTask = await Task.WhenAny(this._completion.Task, Task.Delay(timeout.Value, cancellationToken)).ConfigureAwait(false);
+            if (completedTask != this._completion.Task)
             {
                 this._logger.LogOrchestrationResultTimeout(this.Orchestration, this.Topic);
                 throw new TimeoutException($"Orchestration did not complete within the allowed duration ({timeout}).");
             }
+#endif
         }
 
         this._logger.LogOrchestrationResultComplete(this.Orchestration, this.Topic);

dotnet/src/Agents/UnitTests/Orchestration/OrchestrationResultTests.cs

@@ -77,7 +77,6 @@ public async Task GetValueAsync_WithTimeout_ThrowsTimeoutException_WhenTaskDoesN
 
         // Act & Assert
         TimeoutException exception = await Assert.ThrowsAsync<TimeoutException>(() => result.GetValueAsync(timeout).AsTask());
-        Assert.Contains("Orchestration did not complete within the allowed duration", exception.Message);
     }
 
     [Fact]