Investigate WindowsDesktop dependencies on System.Security.Permissions so it can be safely omitted

While trying to remove `System.Security.Permissions` for https://github.com/dotnet/core-setup/issues/7290, some closure validation errors came up:

```
Assembly 'System.Xaml' is missing dependency 'System.Security.Permissions'
Assembly 'System.Configuration.ConfigurationManager' is missing dependency 'System.Security.Permissions'
Assembly 'System.Security.Cryptography.Xml' is missing dependency 'System.Security.Permissions'
Assembly 'WindowsBase' is missing dependency 'System.Security.Permissions'
Assembly 'System.Windows.Forms.Design.Editors' is missing dependency 'System.Security.Permissions'
Assembly 'System.Drawing' is missing dependency 'System.Security.Permissions'
Assembly 'System.DirectoryServices' is missing dependency 'System.Security.Permissions'
```

Some may be caused by having stale dependencies (https://github.com/dotnet/core-setup/issues/7343), but not all (https://github.com/dotnet/core-setup/pull/7324#discussion_r306436855):

> That's not the only cause for this. Some of these other dependencies are concerning. I suspect we'll need to suppress this, since even once everything is fixed WindowsBase will have typeforwards to System.Security.Permission, but we need to examine all the references before suppressing to find out if there is other work to do to safely omit this.

Once we're sure this is safe (not sure if Core-Setup should be tracking that in particular), we can remove the dependency on `System.Security.Permissions` and add:

```xml

```

/cc @ericstj @vatsan-madhavan