Replace legacy StyleCop(Plus) with StyleCopAnalyzers

Analyzers are enabled in the Debug configuration
only to avoid unnecessary overheads when compiling
normally.

OpenRA.Server/OpenRA.Server.csproj

@@ -14,6 +14,7 @@
     <PlatformTarget>x86</PlatformTarget>
     <ExternalConsole>false</ExternalConsole>
     <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    <CodeAnalysisRuleSet>..\OpenRA.ruleset</CodeAnalysisRuleSet>
   </PropertyGroup>
   <ItemGroup>
     <!-- Work around an issue where Rider does not detect files in the project root using the default glob -->
@@ -28,7 +29,15 @@
     <ProjectReference Include="..\OpenRA.PostProcess\OpenRA.PostProcess.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
     </ProjectReference>
+    <PackageReference Include="StyleCop.Analyzers" Version="1.1.118" />
+    <AdditionalFiles Include="../stylecop.json" />
   </ItemGroup>
+  <Target Name="DisableAnalyzers" BeforeTargets="CoreCompile" Condition="'$(Configuration)'=='Release'">
+    <!-- Disable code style analysis on Release builds to improve compile-time performance -->
+    <ItemGroup Condition="'$(Configuration)'=='Release'">
+      <Analyzer Remove="@(Analyzer)"/>
+    </ItemGroup>
+  </Target>
   <Target Name="PostProcess" AfterTargets="Build" Inputs="$(TargetPath)" Outputs="$(IntermediateOutputPath)\$(TargetFileName).processed">
     <Exec Command="$(TargetDir)/OpenRA.PostProcess.exe $(TargetPath) -LAA" />
     <Touch Files="$(IntermediateOutputPath)\$(TargetFileName).processed" AlwaysCreate="true" />