Upgrade packages to the latest versions

Author: ValeraFinebits

payjoin-ffi/csharp/Payjoin.Tests.csproj

@@ -10,12 +10,12 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageReference Include="xunit" Version="2.6.2" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.4">
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
+    <PackageReference Include="xunit.v3" Version="3.2.2" />
   </ItemGroup>
 
   <!-- Include native library - copied to output directory for testing -->