Use Diacritical.Net library for NameFirstCharacter token

(cherry picked from commit 59ea524e0ce85333779f430b867e93aae366289f)

Closes #4230

src/NzbDrone.Core.Test/OrganizerTests/FileNameBuilderTests/ArtistNameFirstCharacterFixture.cs

@@ -42,6 +42,7 @@ namespace NzbDrone.Core.Test.OrganizerTests.FileNameBuilderTests
         [TestCase("¡Mucha Lucha!", "M", "¡Mucha Lucha!")]
         [TestCase(".hack", "H", "hack")]
         [TestCase("Ütopya", "U", "Ütopya")]
+        [TestCase("Æon Flux", "A", "Æon Flux")]
         public void should_get_expected_folder_name_back(string title, string parent, string child)
         {
             _artist.Name = title;

src/NzbDrone.Core/Lidarr.Core.csproj

@@ -4,6 +4,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Dapper" Version="2.0.123" />
+    <PackageReference Include="Diacritical.Net" Version="1.0.4" />
     <PackageReference Include="System.Text.Json" Version="6.0.8" />
     <PackageReference Include="System.Memory" Version="4.5.5" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.1" />

src/NzbDrone.Core/Organizer/FileNameBuilder.cs

@@ -4,6 +4,7 @@ using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Text.RegularExpressions;
+using Diacritical;
 using NLog;
 using NzbDrone.Common.Cache;
 using NzbDrone.Common.Disk;
@@ -268,13 +269,13 @@ namespace NzbDrone.Core.Organizer
         {
             if (char.IsLetterOrDigit(title[0]))
             {
-                return title.Substring(0, 1).ToUpper().RemoveAccent();
+                return title.Substring(0, 1).ToUpper().RemoveDiacritics()[0].ToString();
             }
 
             // Try the second character if the first was non alphanumeric
             if (char.IsLetterOrDigit(title[1]))
             {
-                return title.Substring(1, 1).ToUpper().RemoveAccent();
+                return title.Substring(1, 1).ToUpper().RemoveDiacritics()[0].ToString();
             }
 
             // Default to "_" if no alphanumeric character can be found in the first 2 positions