MDEV-22535 TABLE::initialize_quick_structures() takes 0.5% in oltp_read_only

- Removed not needed bzero in void TABLE::initialize_quick_structures().
- Replaced bzero with TRASH_ALLOC() to have this change verfied with
  memory checkers
- Added missing table->quick_keys.is_set in table_cond_selectivity()

sql/sql_select.cc

@@ -8573,7 +8573,7 @@ double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s,
     /*
       Check if we have a prefix of key=const that matches a quick select.
     */
-    if (!is_hash_join_key_no(key))
+    if (!is_hash_join_key_no(key) && table->quick_keys.is_set(key))
     {
       key_part_map quick_key_map= (key_part_map(1) << table->quick_key_parts[key]) - 1;
       if (table->quick_rows[key] && 

sql/table.cc

@@ -9358,10 +9358,10 @@ bool TABLE::export_structure(THD *thd, Row_definition_list *defs)
 
 void TABLE::initialize_quick_structures()
 {
-  bzero(quick_rows, sizeof(quick_rows));
-  bzero(quick_key_parts, sizeof(quick_key_parts));
-  bzero(quick_costs, sizeof(quick_costs));
-  bzero(quick_n_ranges, sizeof(quick_n_ranges));
+  TRASH_ALLOC(quick_rows, sizeof(quick_rows));
+  TRASH_ALLOC(quick_key_parts, sizeof(quick_key_parts));
+  TRASH_ALLOC(quick_costs, sizeof(quick_costs));
+  TRASH_ALLOC(quick_n_ranges, sizeof(quick_n_ranges));
 }
 
 /*