Add regression test for: Newlines in metadata are \n instead of \r\n on Windows

[rainersigwald]

Steps to reproduce

Multi-line metadata has changed representation between 15.9.21 and 16.0.360. With this project:

Project file

<Project>
<ItemGroup>
 <I Include="I">
  <M>multiple
  lines
  in
  this
  metadatum</M>
 </I>
</ItemGroup>

<UsingTask TaskName="InlineTask" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll" >
  <ParameterGroup>
    <Files ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true" />
  </ParameterGroup>
  <Task>
    <Using Namespace="System"/>
    <Using Namespace="System.Linq"/>
    <Using Namespace="System.IO"/>
    <Using Namespace="System.Text"/>
    <Code Type="Fragment" Language="cs">
<![CDATA[
    var metadataString = this.Files[0].GetMetadata("M");
    var count = metadataString.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries).Length;

    this.Log.LogMessage(MessageImportance.High, string.Format("Count='{0}'", count));
]]>
    </Code>
  </Task>
</UsingTask>

<Target Name="Go">
 <InlineTask Files="@(I)" />
</Target>

</Project>

Expected behavior

s:\msbuild2>msbuild metadata_newlines.proj
Microsoft (R) Build Engine version 15.9.21+g9802d43bc3 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

  Count='5'

Actual behavior

S:\msbuild2>msbuild metadata_newlines.proj
Microsoft (R) Build Engine version 16.0.360-preview+g9781d96883 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

  Count='1'

[rainersigwald]

This is mitigated by #4213, but we should add a test for it.