[vs17.12] Always respect warning-as-error properties (#10999)

Backport of #10892 to vs17.12

Work item (Internal use): 

### Summary

Respect warning-as-error settings configured per-project when
`-warnaserror` is passed on the command line.

### Customer Impact

Suppressing warnings is unnecessarily complicated and fails for
confusing reasons.

### Regression?

No, this behavior is longstanding, but the severity is higher with NuGet
Audit because NuGet advises configuring warning-as-warning for audit
warning codes.

### Testing

Automated and targeted scenario tests.

### Risk

Low: makes an existing opt-in codepath default.

eng/Versions.props

@@ -2,7 +2,7 @@
 <!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the MIT license. See License.txt in the project root for full license information. -->
 <Project>
   <PropertyGroup>
-    <VersionPrefix>17.12.10</VersionPrefix>
+    <VersionPrefix>17.12.12</VersionPrefix><DotNetFinalVersionKind>release</DotNetFinalVersionKind>
     <DotNetFinalVersionKind>release</DotNetFinalVersionKind>
     <PackageValidationBaselineVersion>17.11.4</PackageValidationBaselineVersion>
     <AssemblyVersion>15.1.0.0</AssemblyVersion>

src/Build/BackEnd/Components/Logging/LoggingService.cs

@@ -1666,8 +1666,8 @@ private void RouteBuildEvent(object loggingEvent)
                 }
             }
 
-            // If this is BuildCheck-ed build - add the warnings promotability/demotability to the service
-            if (buildEventArgs is ProjectStartedEventArgs projectStartedEvent && this._componentHost.BuildParameters.IsBuildCheckEnabled)
+            // Respect warning-promotion properties from the remote project
+            if (buildEventArgs is ProjectStartedEventArgs projectStartedEvent)
             {
                 AddWarningsAsErrors(projectStartedEvent.BuildEventContext, projectStartedEvent.WarningsAsErrors);
                 AddWarningsAsMessages(projectStartedEvent.BuildEventContext, projectStartedEvent.WarningsAsMessages);

src/Build/BackEnd/Components/RequestBuilder/RequestBuilder.cs

@@ -1105,7 +1105,7 @@ private async Task<BuildResult> BuildProject()
         {
             ErrorUtilities.VerifyThrow(_targetBuilder != null, "Target builder is null");
 
-            // We consider this the entrypoint for the project build for purposes of BuildCheck processing 
+            // We consider this the entrypoint for the project build for purposes of BuildCheck processing
             bool isRestoring = _requestEntry.RequestConfiguration.GlobalProperties[MSBuildConstants.MSBuildIsRestoring] is not null;
 
             var buildCheckManager = isRestoring
@@ -1155,7 +1155,7 @@ private async Task<BuildResult> BuildProject()
                     _requestEntry.Request.BuildEventContext);
             }
 
-            
+
             try
             {
                 HandleProjectStarted(buildCheckManager);
@@ -1279,7 +1279,7 @@ private void HandleProjectStarted(IBuildCheckManager buildCheckManager)
             BuildEventContext projectBuildEventContext = _projectLoggingContext?.BuildEventContext;
 
             // We can set the warning as errors and messages only after the project logging context has been created (as it creates the new ProjectContextId)
-            if (buildCheckManager != null && loggingService != null && projectBuildEventContext != null)
+            if (loggingService != null && projectBuildEventContext != null)
             {
                 args.WarningsAsErrors = loggingService.GetWarningsAsErrors(projectBuildEventContext).ToHashSet(StringComparer.OrdinalIgnoreCase);
                 args.WarningsAsMessages = loggingService.GetWarningsAsMessages(projectBuildEventContext).ToHashSet(StringComparer.OrdinalIgnoreCase);

src/Framework/ProjectStartedEventArgs.cs

@@ -335,7 +335,7 @@ public IEnumerable? Items
         }
 
         // Following 3 properties are intended only for internal transfer - to properly communicate the warn as error/msg
-        //  from the worker node, to the main node - that may be producing the buildcheck diagnostics.
+        //  from the worker node, to the main node.
         // They are not going to be in a binlog (at least not as of now).
 
         internal ISet<string>? WarningsAsErrors { get; set; }