Minimize usage of `dotnetbinaries` storage account

[lbussell]

This repo references lots of files from the dotnetbinaries storage account. Wherever possible, we should try to minimize the usage of that storage account.

The various usages are:

• .NET Framework 3.5 installers - can be removed by using Windows Update and/or Features on Demand to install .NET Fx 3.5
  • Use Windows Update and Features on Demand to install .NET Framework 3.5 #1220
• Targeting packs / Reference assemblies for various .NET Framework versions - can all be combined into one file
  • Use combined reference assembly/targeting pack zip file #1217
  • Use NuGet packages to install reference assemblies / targeting packs #1224
• ServiceMonitor.exe - The binary should be re-uploaded as a GitHub release to https://github.com/microsoft/IIS.ServiceMonitor

If we implement all three of these, then we will only have the need for one file (Targeting packs/ref assemblies).

[lbussell]

All dependencies on dotnetbinaries were removed with #1234 and the updated images have been released.