[param-name-importer] Bump to Microsoft.Xml.SgmlReader 1.8.16 (#656)

Microsoft.Xml.SgmlReader 1.8.16 supports .NET Standard 2.0

There is an issue with the new version in that the `lib/netcoreapp3.1`
directory contains both `SgmlReader.exe` and `SgmlReaderDll.dll` and
the `netcoreapp3.1` version of `param-name-importer` tries to consume
the `.exe` file.

Work around this by using `@(PackageReference)` to download the NuGet
but not reference any assembly.  Then we add a `@(Reference)` to the
correct `.dll` and use it.  (We use the `netstandard2.0` version
because both frameworks can use it; `netcoreapp3.1` shouldn't even
exist in the package.)

Fix a warning by changing the `@(System.IO.Compression)` for
`System.IO.Compression` to be conditional on building for (desktop)
.NET Framework, not .NET Core

	Warning MSB3243: No way to resolve conflict between "System.IO.Compression, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" and "System.IO.Compression".
	Choosing "System.IO.Compression, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" arbitrarily.

tools/param-name-importer/param-name-importer.csproj

@@ -9,10 +9,16 @@
   <ItemGroup>
     <!-- Not sure why needed, but only System.IO.Compression.FileSystem.dll is
       included by default, and ZipArchive is type forwarded to System.IO.Compression -->
-    <Reference Include="System.IO.Compression" />
+    <Reference Include="System.IO.Compression" Condition="$(TargetFramework.StartsWith('net4'))" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.Xml.SgmlReader" Version="1.8.14" />
+    <!-- This package erroneously contains /netcoreapp3.1/SgmlReader.exe and /netcoreapp3.1/SgmlReaderDll.dll.
+         We are going to use a package reference to download the nuget, and a regular reference to actually
+         reference the correct assembly. -->
+    <PackageReference Include="Microsoft.Xml.SgmlReader" Version="1.8.16" ExcludeAssets="Compile" GeneratePathProperty="true" />
+    <Reference Include="SgmlReader">
+      <HintPath>$(PkgMicrosoft_Xml_SgmlReader)\lib\netstandard2.0\SgmlReaderDll.dll</HintPath>
+    </Reference>
     <PackageReference Include="Mono.Options" Version="5.3.0.1" />
   </ItemGroup>
   <ItemGroup>