Add IsTestProject property to csproj file

Author: Youssef1313

test/TestAssets/TestProjects/HybridTestRunnerTestProjects/OtherTestProject/OtherTestProject.csproj

@@ -1,11 +1,12 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), testAsset.props))\testAsset.props" />
 
 	<PropertyGroup>
 		<OutputType>Exe</OutputType>
 		<TargetFramework>$(CurrentTargetFramework)</TargetFramework>
 		<ImplicitUsings>enable</ImplicitUsings>
 		<Nullable>enable</Nullable>
+		<IsTestProject>true</IsTestProject>
 		<IsTestingPlatformApplication>true</IsTestingPlatformApplication>
 	</PropertyGroup>