[core] Encapsulate entity preference creation to prepare for hash migration (#13505)

esphome/components/template/datetime/template_datetime.cpp

@@ -18,8 +18,7 @@ void TemplateDateTime::setup() {
     state = this->initial_value_;
   } else {
     datetime::DateTimeEntityRestoreState temp;
-    this->pref_ = global_preferences->make_preference<datetime::DateTimeEntityRestoreState>(
-        194434090U ^ this->get_preference_hash());
+    this->pref_ = this->make_entity_preference<datetime::DateTimeEntityRestoreState>(194434090U);
     if (this->pref_.load(&temp)) {
       temp.apply(this);
       return;