Add new self-profile event for aggregating query hit counts

compiler/rustc_query_impl/src/profiling_support.rs

@@ -259,4 +259,5 @@ pub fn alloc_self_profile_query_strings(tcx: TyCtxt<'_>) {
     for alloc in super::ALLOC_SELF_PROFILE_QUERY_STRINGS.iter() {
         alloc(tcx, &mut string_cache)
     }
+    tcx.sess.prof.store_query_cache_hits();
 }