Moved StringTokenizer to Avalonia.Base.

And make it public instead of linking it from Avalonia.Visuals to Avalonia.Controls.

src/Avalonia.Visuals/Utilities/StringTokenizer.cs → src/Avalonia.Base/Utilities/StringTokenizer.cs

@@ -4,7 +4,7 @@ using static System.Char;
 
 namespace Avalonia.Utilities
 {
-    internal struct StringTokenizer : IDisposable
+    public struct StringTokenizer : IDisposable
     {
         private const char DefaultSeparatorChar = ',';
 

src/Avalonia.Controls/Avalonia.Controls.csproj

@@ -26,7 +26,6 @@
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="..\Avalonia.Visuals\Utilities\StringTokenizer.cs" Link="Utils\StringTokenizer.cs" />
     <Compile Include="..\Shared\SharedAssemblyInfo.cs">
       <Link>Properties\SharedAssemblyInfo.cs</Link>
     </Compile>