Enable warnAsError for correctness builds

[JoeRobich]

These changes setup the Correctness Test leg to fail when the formatting analyzer reports warnings. Other test legs will ignore these warnings and run unit tests as expected. Local builds (.\build.cmd and VS) will report warnings but not fail the build.

[JoeRobich]

Build logs showing a failing correctness build due to formatting errors. Other legs successfully built and started running tests.

src\Workspaces\Core\Portable\AddImports\AbstractAddImportsService.cs(84,1): error IDE0055: (NETCORE_ENGINEERING_TELEMETRY=Build) Fix formatting
src\Workspaces\Core\Portable\AddImports\AbstractAddImportsService.cs(145,121): error IDE0055: (NETCORE_ENGINEERING_TELEMETRY=Build) Fix formatting
src\Compilers\CSharp\Portable\BoundTree\UnboundLambda.cs(620,13): error IDE0055: (NETCORE_ENGINEERING_TELEMETRY=Build) Fix formatting
src\Compilers\CSharp\Portable\BoundTree\UnboundLambda.cs(868,17): error IDE0055: (NETCORE_ENGINEERING_TELEMETRY=Build) Fix formatting
Build failed.
Cmd.exe exited with code '1'.

[JoeRobich]

@sharwell & @jaredpar please take a look

[jaredpar]

Overall looks good. Think we need to also make the following changes:

When building the desktop legs we should not pass warnAsError and should pass skipAnalyzers. That way the desktop leg is focused on running teests while the correctness leg is focused on build correctness including analyzers, formatting, etc ....

https://github.com/dotnet/roslyn/blob/master/azure-pipelines.yml#L40

We should be able to enable MSBuild's warn as error without qualification now here

https://github.com/dotnet/roslyn/blob/master/eng/build.ps1#L231

[JoeRobich]

Build logs showing failing correctness leg

src\Features\CSharp\Portable\SignatureHelp\InitializerExpressionSignatureHelpProvider.cs(25,185): error IDE0055: (NETCORE_ENGINEERING_TELEMETRY=Build) Fix formatting

[JoeRobich]

@jaredpar Did I get those changes right?

[jaredpar]

[RikkiGibson]

I have been instructed by the author to hit the button