Auto merge of #134841 - estebank:serde-attr-4, r=wesleywiser

Look at proc-macro attributes when encountering unknown attribute

```
error: cannot find attribute `sede` in this scope
  --> $DIR/missing-derive-2.rs:22:7
   |
LL |     #[sede(untagged)]
   |       ^^^^
   |
help: the derive macros `Deserialize` and `Serialize` accept the similarly named `serde` attribute
   |
LL |     #[serde(untagged)]
   |         +

error: cannot find attribute `serde` in this scope
  --> $DIR/missing-derive-2.rs:16:7
   |
LL |     #[serde(untagged)]
   |       ^^^^^
   |
note: `serde` is imported here, but it is a crate, not an attribute
  --> $DIR/missing-derive-2.rs:5:1
   |
LL | extern crate serde;
   | ^^^^^^^^^^^^^^^^^^^
help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
   |
LL + #[derive(Serialize, Deserialize)]
LL | enum B {
   |
```

Partially address #47608. This PR doesn't find [macros that haven't yet been imported by name](rust-lang/rust@af945cb).

Author: bors