Update to allow C# 8

Author: sharwell

StyleCop.Analyzers/Directory.Build.props

@@ -10,7 +10,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <LangVersion>7.2</LangVersion>
+    <LangVersion>8</LangVersion>
     <Features>strict</Features>
   </PropertyGroup>
 
@@ -46,7 +46,7 @@
     <PackageReference Include="AsyncUsageAnalyzers" Version="1.0.0-alpha003" PrivateAssets="all" />
     <PackageReference Include="DotNetAnalyzers.DocumentationAnalyzers" Version="1.0.0-beta.46" PrivateAssets="all" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.66" PrivateAssets="all" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.CodeStyle" Version="2.11.0-beta2-63603-03" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.CodeStyle" Version="3.6.0-4.20251.5" PrivateAssets="all" />
   </ItemGroup>
 
   <!-- Public API -->