Provided methods currently don't get type erasure performed on them because they are not in an `impl` block. If we are instantiating a method that is an associated item, but *not* in an impl block, treat it as a provided method instead.
For example, if `trait Foo: Bar`, and we try to call a method from `Bar` on `dyn Foo`, encode the callsite as passing a `dyn Bar`, not a `dyn Foo`.
