Support VS Mac 17.3 preview 3

Xamarin.Mac workload dll renamed to Microsoft.macOS.dll and is now
used in VS mac 17.3 preview 3. Reference Microsoft.macOS.dll
directly from the VS Mac app bundle. The package reference
System.Runtime.InteropServices.NFloat.Internal is needed to get
various implicit conversions from int to NFloat.

Author: mrward

src/MonoDevelop.ProjectSystem.Tools/MonoDevelop.References.props

@@ -1,5 +1,12 @@
 <Project>
   <ItemGroup>
+   <PackageReference Include="System.Runtime.InteropServices.NFloat.Internal" Version="6.0.1" />
+  </ItemGroup>
+  <ItemGroup>
+    <Reference Include="Microsoft.macOS">
+      <HintPath>$(MDBinDir)\Microsoft.macOS.dll</HintPath>
+      <Private>False</Private>
+    </Reference>
     <Reference Include="Mono.Addins">
       <Private>False</Private>
       <HintPath>$(MDBinDir)\Mono.Addins.dll</HintPath>
@@ -24,10 +31,6 @@
       <Private>False</Private>
       <HintPath>$(MDBinDir)\System.Collections.Immutable.dll</HintPath>
     </Reference>
-    <Reference Include="Xamarin.Mac">
-      <HintPath>/usr/local/share/dotnet/packs/Microsoft.macOS.Ref/12.1.301-preview.13.7/ref/net6.0/Xamarin.Mac.dll</HintPath>
-      <Private>False</Private>
-    </Reference>
     <Reference Include="Xwt">
       <Private>False</Private>
       <HintPath>$(MDBinDir)\Xwt.dll</HintPath>