tests: Move run-pass tests without naming conflicts to ui

src/test/ui/format-ref-cell.rs

@@ -0,0 +1,10 @@
+// run-pass
+
+use std::cell::RefCell;
+
+pub fn main() {
+    let name = RefCell::new("rust");
+    let what = RefCell::new("rocks");
+    let msg = format!("{name} {}", &*what.borrow(), name=&*name.borrow());
+    assert_eq!(msg, "rust rocks".to_string());
+}