Use no row factory in TypeInfo.fetch*()

Use no row factory in TypeInfo.fetch*()

TypeInfo.fetch() and TypeInfo.fetch_async() delegate results processing
to TypeInfo._fetch() which only handle results as tuples. Therefore, we
build the cursor with no row factory to guarantee this. Still we need to
add a type hint on 'recs' variable because this cannot be inferred (this
fixes the mypy error introduced in previous commits).