When targeting .NET Framework, the SDK references System.IO.Compression.FileSystem, but not System.IO.Compression

[terrajobst]

I don't know why we did this, but it doesn't really make sense:

System.IO.Compression.FileSystem defines the ZipFile class which has convenience methods for ZipArchive that allow using paths instead of Stream. We did this originally for Windows 8 because you couldn't use paths in store apps. Since ZipArchive is defined in System.IO.Compression and is returned from various methods on ZipFile, users will usually get a compilation error:

The type 'ZipArchive' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.IO.Compression, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'

Regardless of the comment here:

sdk/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.BeforeCommon.targets

Lines 160 to 161 in 5e9972a

	<!-- Framework assemblies introduced in .NET 4.5 -->
	<_SDKImplicitReference Include="System.IO.Compression.FileSystem" Condition=" '$(_TargetFrameworkVersionWithoutV)' >= '4.5' "/>

it doesn't seem old-style (i.e. non-SDK style) projects add an assembly reference to System.IO.Compression.FileSystem.

Comparing what an old-style .NET Framework 4.7.2 project references it seems there are quite a few inconsistencies:

Assembly	Referenced in old-style	Referenced in SDK-style
Microsoft.CSharp	Yes	No
mscorlib	Yes	Yes
System	Yes	Yes
System.Core	Yes	Yes
System.Data	Yes	Yes
System.Data.DataSetExtensions	Yes	No
System.Drawing	No	Yes
System.IO.Compression.FileSystem	No	Yes
System.Net.Http	Yes	No
System.Numerics	No	Yes
System.Runtime.Serialization	No	Yes
System.Xml	Yes	Yes
System.Xml.Linq	Yes	Yes

At the minimum, we should add System.IO.Compression to make the references consistent but we might also want to add some of the missing ones, most notably System.Net.Http.