Disallow (borrow $t) in function result types (#1162)

This is something I forgot to implement in the intial implementation of
resources. Validation in the component model dictates that `(borrow $t)`
cannot be returned at this time, however, so this implements the
necessary validation for this predicate.

This commit modifies the calculation of a type's size to instead
calculate a `TypeInfo` where that embeds both the size and
borrow-related information. A check when translating function types is
then added to ensure that all function result types do not contain
borrows.

Author: alexcrichton