04128982ff
Prevent some attributes from being merged with others on reexports Final fix for https://github.com/rust-lang/rust/issues/59368. As discussed on zulip [here](https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Filtering.20sub.20attributes.20in.20ast.3A.3AAttribute), we need to clone the `Attribute` to be able to filter some parts of it. Then we need to go through the attributes to able to only keep what we want (everything except a few attributes in short). As for the second commit, when I wrote the test, I realized that the code to traverse all reexports one by one to collect all their attributes was not completely working so I fixed the few issues remaining. r? `@notriddle`