Turn on TreatWarningsAsErrors since they are currently harmless (#32166)

* Turn on TreatWarningsAsErrors since they are currently harmless

* Only treat ILLinker errors as warnings

src/Hosting/test/FunctionalTests/LinkedApplicationTests.cs

@@ -13,7 +13,6 @@ namespace Microsoft.AspNetCore.Hosting.FunctionalTests
 {
     public class LinkedApplicationTests : LoggedTest
     {
-        [QuarantinedTest("https://github.com/dotnet/aspnetcore/issues/24755")]
         [Fact]
         public async Task LinkedApplicationWorks()
         {

src/Hosting/test/testassets/BasicLinkedApp/BasicLinkedApp.csproj

@@ -5,6 +5,7 @@
     <OutputType>Exe</OutputType>
     <PublishTrimmed>true</PublishTrimmed>
     <TrimMode>link</TrimMode>
+    <ILLinkTreatWarningsAsErrors>false</ILLinkTreatWarningsAsErrors>
   </PropertyGroup>
 
   <ItemGroup>