Bug 1550860 - Mark implicit builtinclass interfaces explicitly. r=nika

If an XPIDL interface has a method or attribute that is [notxpcom],
then it is implicitly treated as [builtinclass], even if it is not
marked as such. For clarity, this patch goes through and marks every
place that relies on this behavior (aside from some test code).

Differential Revision: https://phabricator.services.mozilla.com/D30714

--HG--
extra : moz-landing-system : lando