Could we use Parallel to improve the Walk performance in Kestrel ConnectionManager?

[WeihanLi]

There's the Walk method source in ConnectionManager, you can get details from https://github.com/dotnet/aspnetcore/blob/v5.0.0/src/Servers/Kestrel/Core/src/Internal/Infrastructure/ConnectionManager.cs#L55

public void Walk(Action<KestrelConnection> callback)
{
	foreach (var kvp in _connectionReferences)
	{
		var reference = kvp.Value;

		if (reference.TryGetConnection(out var connection))
		{
			callback(connection);
		}
		else if (_connectionReferences.TryRemove(kvp.Key, out reference))
		{
			// It's safe to modify the ConcurrentDictionary in the foreach.
			// The connection reference has become unrooted because the application never completed.
			_trace.ApplicationNeverCompleted(reference.ConnectionId);
			reference.StopTrasnsportTracking();
		}

		// If both conditions are false, the connection was removed during the heartbeat.
	}
}

Since the _connectionReferences is a ConcurrentDictionary, so could we use Parallel instead foreach loop sequentially?

[WeihanLi]

Created issue for better tracking experience #27931