`non_exhaustive_omitted_patterns` is missing span

[Noratrieb]

Currently, I get the following error message:

error: some variants are not matched explicitly
   |
note: the lint level is defined here
  --> selene-lib/src/rules/high_cyclomatic_complexity.rs:77:14
   |
77 |         deny(non_exhaustive_omitted_patterns)
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: ensure that all variants are matched explicitly by adding the suggested match arms
   = note: the matched value is of type `full_moon::ast::Value` and the `non_exhaustive_omitted_patterns` attribute was found

error: some variants are not matched explicitly
  |
  = help: ensure that all variants are matched explicitly by adding the suggested match arms
  = note: the matched value is of type `full_moon::ast::Expression` and the `non_exhaustive_omitted_patterns` attribute was found

error: some variants are not matched explicitly
    |
note: the lint level is defined here
   --> selene-lib/src/rules/high_cyclomatic_complexity.rs:180:18
    |
180 |             deny(non_exhaustive_omitted_patterns)
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: ensure that all variants are matched explicitly by adding the suggested match arms
    = note: the matched value is of type `full_moon::ast::Stmt` and the `non_exhaustive_omitted_patterns` attribute was found

error: could not compile `selene-lib` due to 3 previous errors

This error message is correct, but not helpful, and confused the person writing the pull request who hit this issue. It does not show what the variants are or where the match is. I would file a repro but I'm fairly sure non_exhaustive is ignored in the same crate, so it would not be doable on playground.

Originally posted by @Kampfkarren in #89554 (comment)

[Noratrieb]

I hit this today when matching on syn::Item, so it's still around. The lint also doesn't mention which variants were not covered, which is pretty hard to debug (I had to manually compare my match with the enum definition).

[clubby789]

This doesn't seem to trigger for smaller examples, so I'll try and minimize the issue