Fix wrong spans with external macros in the `dropping_copy_types` lint
This PR fixes some wrong spans manipulations when external macros are involved.
Specifically we didn't make sure the spans had the same context, which kind-of make our spans manipulations go wrong and produce weird spans. We fix that by making sure they have the same context.
Fixes https://github.com/rust-lang/rust/issues/145427
c97a9c82b2