V12: Update ImageSharp V3 and Add Legacy V2 Project (#14216)

* Rename old imagesharp to v2

* Add Ronalds PR as imagesharp

* Ensure that we use V3 by default

src/Umbraco.Cms.Imaging.ImageSharp/ConfigureImageSharpMiddlewareOptions.cs

@@ -2,7 +2,6 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Headers;
 using Microsoft.Extensions.Options;
 using Microsoft.Net.Http.Headers;
-using SixLabors.ImageSharp;
 using SixLabors.ImageSharp.Web.Commands;
 using SixLabors.ImageSharp.Web.Middleware;
 using SixLabors.ImageSharp.Web.Processors;