MDEV-11706 Assertion `is_stat_field || !table || (!table->write_set || bitmap_is_set(table->write_set, field_index) || (table->vcol_set && bitmap_is_set(table->vcol_set, field_index)))' failed in Field_time::store_TIME_with_warning

vcols and triggers. Revert 094f4cf7,
backport the correct fix (Table_triggers_list::mark_fields_used() not
marking vcols) from 10.2.