Auto merge of #129183 - estebank:cfg-visitor, r=davidtwco

Detect more `cfg`d out items in resolution errors

Use a visitor to collect *all* items (including those nested) that were stripped behind a `cfg` condition.

```
error[E0425]: cannot find function `f` in this scope
  --> $DIR/nested-cfg-attrs.rs:4:13
   |
LL | fn main() { f() }
   |             ^ not found in this scope
   |
note: found an item that was configured out
  --> $DIR/nested-cfg-attrs.rs:2:4
   |
LL | fn f() {}
   |    ^
note: the item is gated here
  --> $DIR/nested-cfg-attrs.rs:1:35
   |
LL | #[cfg_attr(all(), cfg_attr(all(), cfg(FALSE)))]
   |                                   ^^^^^^^^^^
```

1 files changed, 2 insertions, 5 deletions

diff --git a/tests/ui/macros/macro-outer-attributes.stderr b/tests/ui/macros/macro-outer-attributes.stderr
index 9215754d4bb..4696bb774e3 100644
--- a/tests/ui/macros/macro-outer-attributes.stderr
+++ b/tests/ui/macros/macro-outer-attributes.stderr
@@ -7,13 +7,10 @@ LL |     a::bar();
 note: found an item that was configured out
   --> $DIR/macro-outer-attributes.rs:9:14
    |
+LL |       #[cfg(false)],
+   |             ----- the item is gated here
 LL |       pub fn bar() { });
    |              ^^^
-note: the item is gated here
-  --> $DIR/macro-outer-attributes.rs:8:13
-   |
-LL |       #[cfg(false)],
-   |             ^^^^^
 help: consider importing this function
    |
 LL + use b::bar;