Obsolete old APIs (in ref and impl assemblies)

#10544 exposes the new APIs but does not obsolete the GetData* APIs.

See WinForms obsoletions here https://github.com/dotnet/winforms/blob/89978450ea81fbaffb3e41ab3a2e131aba22e09f/src/System.Windows.Forms/System/Windows/Forms/OLE/Clipboard.cs#L135-L147 and here https://github.com/dotnet/winforms/blob/89978450ea81fbaffb3e41ab3a2e131aba22e09f/src/System.Windows.Forms/System/Windows/Forms/OLE/DataObject.cs#L108-L127.

``` C#
///
/// Retrieves data from the in the specified format.
///
///
/// The current thread is not in single-threaded apartment (STA) mode.
///
[Obsolete(
Obsoletions.ClipboardGetDataMessage,
error: false,
DiagnosticId = Obsoletions.ClipboardGetDataDiagnosticId,
UrlFormat = Obsoletions.SharedUrlFormat)]
public static object? GetData(string format) =>
string.IsNullOrWhiteSpace(format) ? null : GetData(format, autoConvert: false);
```