[Windows] Handle non-seekable streams in PlatformImage.FromStream

[MartyIX]

Description of Change

AsRandomAccessStream throws NotSupportedException when the stream is not seekable. This PR is a simple workaround for it.

The second commit adds an optimization. The idea is to remove AsyncPump (introduced in dotnet/Microsoft.Maui.Graphics@4597923 and merged to MAUI in #8739) which does not seem to be necessary at all. I have tested the change with parallel loading of images and it did not break for me. But then again I don't really know why AsyncPump was introduced in the first place. This commit is an alternative to #23624 approach and the improvement should be the same as in that PR: #23624 (comment) (9 seconds -> 1.3 seconds for a batch of images containing ~100 images).

Test

Tested with provided sample code:

using Microsoft.Maui.Graphics.Platform;

namespace Maui.Controls.Sample;

public partial class MainPage : ContentPage
{
	public MainPage()
	{
		InitializeComponent();
	}

	private async void OnCounterClicked(object sender, EventArgs e)
	{
		try
		{
			var imageUrl = "https://cdn-dynmedia-1.microsoft.com/is/image/microsoftcorp/Highlight-Surface-Laptop-AI-7Ed-Sapphire-MC001-3000x1682:VP5-1920x600";
			var stream = await new HttpClient().GetStreamAsync(imageUrl);
			var img = PlatformImage.FromStream(stream);
		}
		catch (Exception ex)
		{
			Console.WriteLine(ex);
		}

	}
}

Issues Fixed

Fixes #18954

[dotnet-policy-service]

Hey there @MartyIX! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[mattleibow]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[mattleibow]

Not sure if you have to first reset the memory stream position to 0?

[MartyIX]

Yes, you are right, it's documented: https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.copyto?view=net-8.0#definition and I verified it experimentally.

Fixed by adding the third commit.

[PureWeen]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[MartyIX]

@mattleibow Could you please take a look?

[MartyIX]

Closing in favor of #23824.