Use Verify.Xunit instead of ApprovalTests

The VerifyTests API when using a theory is easier to use than the ApprovalTests.

Also, the Public API approval test is much easier to write thanks to the `UseFileName` method.

Author: 0xced

tests/Log4NetTextFormatterTest.CustomLogEventPropertyValue.approved.xml renamed to tests/Log4NetTextFormatterTest.CustomLogEventPropertyValue.verified.xml

@@ -1,31 +1,18 @@
-using System.IO;
-using System.Reflection;
-using ApprovalTests;
-using ApprovalTests.Namers;
-using ApprovalTests.Reporters;
+using System.Threading.Tasks;
 using PublicApiGenerator;
+using VerifyXunit;
 using Xunit;
 
 namespace Serilog.Formatting.Log4Net.Tests
 {
+    [UsesVerify]
     public class PublicApi
     {
         [Fact]
-        public void ApprovePublicApi()
+        public Task ApprovePublicApi()
         {
-            var assembly = typeof(Log4NetTextFormatter).Assembly;
-            var publicApi = assembly.GeneratePublicApi();
-            var writer = new ApprovalTextWriter(publicApi);
-            Approvals.Verify(writer, new AssemblyNamer(assembly), DiffReporter.INSTANCE);
-        }
-
-        private class AssemblyNamer : UnitTestFrameworkNamer
-        {
-            private readonly Assembly _assembly;
-
-            public AssemblyNamer(Assembly assembly) => _assembly = assembly;
-
-            public override string Name => nameof(PublicApi) + "." + Path.GetFileNameWithoutExtension(_assembly.Location);
+            var publicApi = typeof(Log4NetTextFormatter).Assembly.GeneratePublicApi();
+            return Verifier.Verify(publicApi).UseFileName("PublicApi");
         }
     }
 }

tests/Log4NetTextFormatterTest.DefaultFormatProvider.approved.xml renamed to tests/Log4NetTextFormatterTest.DefaultFormatProvider.verified.xml

@@ -8,14 +8,14 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="ApprovalTests" Version="5.7.0" />
     <PackageReference Include="coverlet.msbuild" Version="3.1.0" PrivateAssets="all" />
     <PackageReference Include="FluentAssertions" Version="6.1.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
     <PackageReference Include="ReportGenerator" Version="4.8.12" />
     <PackageReference Include="Serilog.Enrichers.Environment" Version="2.2.0" />
     <PackageReference Include="Serilog.Enrichers.Thread" Version="3.1.0" />
+    <PackageReference Include="Verify.Xunit" Version="13.3.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
   </ItemGroup>