Add clean metrics (#20410)

runtime/src/accounts_index.rs

@@ -571,6 +571,8 @@ pub struct AccountsIndexRootsStats {
     pub roots_range: u64,
     pub rooted_cleaned_count: usize,
     pub unrooted_cleaned_count: usize,
+    pub clean_unref_from_storage_us: u64,
+    pub clean_dead_slot_us: u64,
 }
 
 pub struct AccountsIndexIterator<'a, T: IndexValue> {
@@ -1805,6 +1807,8 @@ impl<T: IndexValue> AccountsIndex<T> {
             roots_range,
             rooted_cleaned_count: 0,
             unrooted_cleaned_count: 0,
+            clean_unref_from_storage_us: 0,
+            clean_dead_slot_us: 0,
         })
     }