Fix exception in Kafka on .NET Framework (#8366)

## Summary of changes

Ran Kafka locally as I was attempting to port it to Testcontainers and
was actually get exceptions / errors on it, this resolves them (or at
least it seems to resolve them). Also noticed them in Error Tracking,
but only a single instance, but I'm not 100% sure if it was the same,
Error Tracking is linked in the linked Jira Ticket.

## Reason for change

Previously this was using `IsCompletedSuccessfully` and then doing a
cast and enumeration of all properties and was failing with the
following error as `IsCompletedSuccessfully` isn't available on .NET
Framework:

```
2026-03-24 15:43:11.768 -04:00 [WRN] Error extracting cluster_id from Kafka metadata Datadog.Trace.DuckTyping.DuckTypePropertyOrFieldNotFoundException: The property or field 'IsCompletedSuccessfully' for the proxy property 'IsCompletedSuccessfully' was not found in the instance of type 'System.Threading.Tasks.Task`1[[Confluent.Kafka.Admin.DescribeClusterResult, Confluent.Kafka, Version=2.6.1.0, Culture=neutral, PublicKeyToken=12c514ca49093d1e]]'.
   at Datadog.Trace.DuckTyping.DuckTypePropertyOrFieldNotFoundException.Throw(String name, String duckAttributeName, Type type)
   at Datadog.Trace.DuckTyping.DuckType.CreateProperties(TypeBuilder proxyTypeBuilder, Type proxyDefinitionType, Type targetType, FieldInfo instanceField)
   at Datadog.Trace.DuckTyping.DuckType.CreateProxyType(Type proxyDefinitionType, Type targetType, Boolean dryRun)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Datadog.Trace.DuckTyping.DuckType.CreateTypeResult.ThrowOnError[T](Object instance)
   at Datadog.Trace.DuckTyping.DuckType.CreateTypeResult.CreateInstance[T](Object instance)
   at Datadog.Trace.DuckTyping.DuckType.CreateCache`1.Create(Object instance)
   at Datadog.Trace.ClrProfiler.AutoInstrumentation.Kafka.KafkaHelper.DescribeClusterWithTimeout(IAdminClient adminClient, Type describeClusterOptionsType)
   at Datadog.Trace.ClrProfiler.AutoInstrumentation.Kafka.KafkaHelper.GetClusterId(String bootstrapServers, Object clientInstance)
 { MachineName: ".", Process: "[59476 Samples.Kafka]", AppDomain: "[1 Samples.Kafka.exe]", TracerVersion: "3.41.0.0" }
```

## Implementation details

Remove `IsCompletedSuccessfully` from `IDuckTypeTask` as it isn't there
on .NET Framework, attempted initially to go with TaskStatus but this
caused failures for xUnit/MS Test integration tests as those appear to
be using ValueTask, which doesn't have it.

Removing `IsCompletedSuccessfully` required some more changes to
`KafkaHelper`

## Test coverage

Applied the fix, re-ran didn't see again, however, the Error Tracking
one may be a different bug as it appears that it is on .NET 9.0 😕

Edit: yes appears to be a different error that came up during
development that was addressed

## Other details
<!-- Fixes #{issue} -->

Fixes https://datadoghq.atlassian.net/browse/APMLP-1146
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Author: bouwkast

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/Kafka/KafkaHelper.cs

@@ -462,32 +462,20 @@ internal static void TryInjectHeaders<TTopicPartitionMarker, TMessage>(
             options.DuckCast<IDescribeClusterOptions>().RequestTimeout = TimeSpan.FromSeconds(2);
 
             var duckTask = adminClient.DescribeClusterAsync(options);
-            var describeResult = SafeGetResult<IDuckTypeTask<IDescribeClusterResult>, IDescribeClusterResult>(duckTask);
-            return describeResult?.ClusterId;
 
-            static TResult? SafeGetResult<TTask, TResult>(TTask task)
-                where TTask : IDuckTypeTask<TResult>
-                where TResult : IDescribeClusterResult
+            var originalContext = SynchronizationContext.Current;
+            try
             {
-                if (task.IsCompletedSuccessfully)
-                {
-                    return task.Result;
-                }
-
-                var originalContext = SynchronizationContext.Current;
-                try
-                {
-                    // Set the synchronization context to null to avoid deadlocks.
-                    SynchronizationContext.SetSynchronizationContext(null);
+                // Set the synchronization context to null to avoid deadlocks.
+                SynchronizationContext.SetSynchronizationContext(null);
 
-                    // Wait synchronously for the task to complete.
-                    return task.GetAwaiter().GetResult();
-                }
-                finally
-                {
-                    // Restore the original synchronization context.
-                    SynchronizationContext.SetSynchronizationContext(originalContext);
-                }
+                // Wait synchronously for the task to complete.
+                return duckTask.GetAwaiter().GetResult()?.ClusterId;
+            }
+            finally
+            {
+                // Restore the original synchronization context.
+                SynchronizationContext.SetSynchronizationContext(originalContext);
             }
         }
 

tracer/src/Datadog.Trace/DuckTyping/IDuckTypeTask.cs

@@ -12,11 +12,6 @@ namespace Datadog.Trace.DuckTyping;
 /// <typeparam name="T">Type of the result</typeparam>
 public interface IDuckTypeTask<out T> : IDuckType
 {
-    /// <summary>
-    /// Gets a value indicating whether if the task is completed
-    /// </summary>
-    bool IsCompletedSuccessfully { get; }
-
     /// <summary>
     /// Gets the result of the task
     /// </summary>
@@ -34,11 +29,6 @@ public interface IDuckTypeTask<out T> : IDuckType
 /// </summary>
 public interface IDuckTypeTask : IDuckType
 {
-    /// <summary>
-    /// Gets a value indicating whether if the task is completed
-    /// </summary>
-    bool IsCompletedSuccessfully { get; }
-
     /// <summary>
     /// Gets the awaiter for the task
     /// </summary>