Revert "Make ImageSourcePartExtensions public"

[mattleibow]

Reverts #16633

This API needs more design as there are some issues, and the correct/current way is:

maui/src/Core/src/ImageSources/ImageSourceExtensions.cs

Lines 21 to 62 in 9fea1f5

	public static partial class ImageSourceExtensions
	{
	public static void LoadImage(this IImageSource? source, IMauiContext mauiContext, Action<IImageSourceServiceResult<PlatformImage>?>? finished = null)
	{
	LoadImageResult(source.GetPlatformImageAsync(mauiContext), finished)
	.FireAndForget(mauiContext.Services.CreateLogger<IImageSource>(), nameof(LoadImage));
	}
	static async Task LoadImageResult(Task<IImageSourceServiceResult<PlatformImage>?> task, Action<IImageSourceServiceResult<PlatformImage>?>? finished = null)
	{
	var result = await task;
	finished?.Invoke(result);
	}
	public static Task<IImageSourceServiceResult<PlatformImage>?> GetPlatformImageAsync(this IImageSource? imageSource, IMauiContext mauiContext)
	{
	if (imageSource == null)
	return Task.FromResult<IImageSourceServiceResult<PlatformImage>?>(null);
	var services = mauiContext.Services;
	var provider = services.GetRequiredService<IImageSourceServiceProvider>();
	var imageSourceService = provider.GetRequiredImageSourceService(imageSource);
	return imageSourceService.GetPlatformImageAsync(imageSource, mauiContext);
	}
	public static Task<IImageSourceServiceResult<PlatformImage>?> GetPlatformImageAsync(this IImageSourceService imageSourceService, IImageSource? imageSource, IMauiContext mauiContext)
	{
	if (imageSource == null)
	return Task.FromResult<IImageSourceServiceResult<PlatformImage>?>(null);
	#if IOS || MACCATALYST
	return imageSourceService.GetImageAsync(imageSource);
	#elif ANDROID
	return imageSourceService.GetDrawableAsync(imageSource, mauiContext.Context!);
	#elif WINDOWS
	return imageSourceService.GetImageSourceAsync(imageSource);
	#elif TIZEN
	return imageSourceService.GetImageAsync(imageSource);
	#else
	throw new NotImplementedException();
	#endif
	}