Generate defaulted foundation feature dependencies

[kennykerr]

@ChrisDenton suggested we automatically include the Foundation and Win32_Foundation features for WinRT and Win32 APIs respectively. This seems like a good change to reduce unnecessary code gen and feature requirements.

See the changes to samples for the usability: fed889e

Also this for the reduction in code gen:

Fixes: #2717 (comment)

[ChrisDenton]

Obviously I'm very much in favour of the idea behind this change!

Browsing through the generated docs, it does seem to simplify things a lot. Perhaps less so when there's already a lot of features required for an item but even then it's one less thing for the user to think about.

[kennykerr]

Yep, I noticed that there are tens of thousands of cfg attributes that only require either Win32_Foundation or Foundation so this seems like an obvious win.