Rollup merge of #80944 - LingMan:map_or, r=nagisa

Use Option::map_or instead of `.map(..).unwrap_or(..)`

``@rustbot`` modify labels +C-cleanup +T-compiler

compiler/rustc_mir/src/monomorphize/partitioning/mod.rs

@@ -247,8 +247,7 @@ where
             for (mono_item, linkage) in cgu.items() {
                 let symbol_name = mono_item.symbol_name(tcx).name;
                 let symbol_hash_start = symbol_name.rfind('h');
-                let symbol_hash =
-                    symbol_hash_start.map(|i| &symbol_name[i..]).unwrap_or("<no hash>");
+                let symbol_hash = symbol_hash_start.map_or("<no hash>", |i| &symbol_name[i..]);
 
                 debug!(
                     " - {} [{:?}] [{}] estimated size {}",