[wasm] Pass --web-server-use-cop for threading samples (#76419)

* [wasm] Pass --web-server-use-cop for threading samples

* CI: Add wasm samples to wasm specific paths list

eng/pipelines/common/evaluate-default-paths.yml

@@ -12,6 +12,7 @@ parameters:
         src/libraries/sendtohelix-wasm.targets
         src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/*
         src/mono/nuget/Microsoft.NET.Runtime.wasm.Sample.Mono/*
+        src/mono/sample/wasm/*
         src/mono/wasi/*
         src/mono/wasm/*
         src/tasks/WasmAppBuilder/*

src/mono/sample/wasm/Directory.Build.targets

@@ -7,6 +7,7 @@
     <RunScriptInputName Condition="'$(TargetOS)' == 'Browser' and '$(OS)' == 'Windows_NT'">WasmRunnerTemplate.cmd</RunScriptInputName>
 
     <RunScriptOutputPath>$([MSBuild]::NormalizePath('$(WasmAppDir)', '$(RunScriptOutputName)'))</RunScriptOutputPath>
+    <WasmXHarnessArgs Condition="'$(WasmEnableThreads)' == 'true' or '$(WasmEnablePerfTracing)' == 'true' or '$(MonoWasmBuildVariant)' == 'perftrace' or '$(MonoWasmBuildVariant)' == 'multithread'">$(WasmXHarnessArgs) --web-server-use-cop</WasmXHarnessArgs>
   </PropertyGroup>
 
   <Target Name="BuildSampleInTree"