Rollup merge of #89867 - Urgau:fix-double-definition, r=GuillaumeGomez

Fix macro_rules! duplication when reexported in the same module

This can append if within the same module a `#[macro_export] macro_rules!`
is declared but also a reexport of itself producing two export of the same
macro in the same module. In that case we only want to document it once.

Before:
```
Module {
    is_crate: true,
    items: [
        Id("0:4"),   // pub use crate::repro as repro2;
        Id("0:3"),   // macro_rules! repro
        Id("0:3"),   // duplicate, same as above
    ],
}
```

After:
```
Module {
    is_crate: true,
    items: [
        Id("0:4"),   // pub use crate::repro as repro2;
        Id("0:3"),   // macro_rules! repro
    ],
}
```

Fixes https://github.com/rust-lang/rust/issues/89852

src/test/rustdoc-json/reexport/macro.rs

@@ -0,0 +1,17 @@
+// edition:2018
+
+#![no_core]
+#![feature(no_core)]
+
+// @count macro.json "$.index[*][?(@.name=='macro')].inner.items[*]" 2
+
+// @set repro_id = macro.json "$.index[*][?(@.name=='repro')].id"
+// @has - "$.index[*][?(@.name=='macro')].inner.items[*]" $repro_id
+#[macro_export]
+macro_rules! repro {
+    () => {};
+}
+
+// @set repro2_id = macro.json "$.index[*][?(@.inner.name=='repro2')].id"
+// @has - "$.index[*][?(@.name=='macro')].inner.items[*]" $repro2_id
+pub use crate::repro as repro2;

src/test/rustdoc/issue-89852.rs

@@ -0,0 +1,14 @@
+// edition:2018
+
+#![no_core]
+#![feature(no_core)]
+
+// @matches 'issue_89852/sidebar-items.js' '"repro"'
+// @!matches 'issue_89852/sidebar-items.js' '"repro".*"repro"'
+
+#[macro_export]
+macro_rules! repro {
+    () => {};
+}
+
+pub use crate::repro as repro2;