rustdoc: rename issue-\d+.rs tests to have meaningful names

tests/rustdoc/multiple-macro-rules-w-same-name-submodule-99221.rs

@@ -0,0 +1,20 @@
+//@ aux-build:issue-99221-aux.rs
+//@ build-aux-docs
+//@ ignore-cross-compile
+
+// https://github.com/rust-lang/rust/issues/99221
+#![crate_name = "foo"]
+
+#[macro_use]
+extern crate issue_99221_aux;
+
+pub use issue_99221_aux::*;
+
+// @count foo/index.html '//a[@class="macro"]' 1
+
+mod inner {
+    #[macro_export]
+    macro_rules! print {
+        () => ()
+    }
+}