Add GetAllBytesAsync to AbpFormFileExtensions

This makes it easier to get an array of bytes directly from an `IFormFile`

framework/src/Volo.Abp.AspNetCore.Mvc/Microsoft/AspNetCore/Http/AbpFormFileExtensions.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNetCore.Http
 {
@@ -11,5 +12,11 @@ namespace Microsoft.AspNetCore.Http
                 return stream.GetAllBytes();
             }
         }
+
+        public static async Task<byte[]> GetAllBytesAsync(this IFormFile file)
+        {
+            using var stream = file.OpenReadStream();
+            return await stream.GetAllBytesAsync();
+        }
     }
 }