Rollup merge of #126717 - nnethercote:rustfmt-use-pre-cleanups, r=jieyouxu

Clean up some comments near `use` declarations

#125443 will reformat all `use` declarations in the repository. There are a few edge cases involving comments on `use` declarations that require care. This PR cleans up some clumsy comment cases, taking us a step closer to #125443 being able to merge.

r? ``@lqd``

Author: matthiaskrgr