[select] Refactor to index-based operations for immediate and future RAM savings (#11623)

esphome/components/template/select/template_select.cpp

@@ -24,7 +24,7 @@ void TemplateSelect::setup() {
     ESP_LOGD(TAG, "State from initial: %s", this->option_at(index));
   }
 
-  this->publish_state(this->at(index).value());
+  this->publish_state(index);
 }
 
 void TemplateSelect::update() {
@@ -41,16 +41,14 @@ void TemplateSelect::update() {
   }
 }
 
-void TemplateSelect::control(const std::string &value) {
-  this->set_trigger_->trigger(value);
+void TemplateSelect::control(size_t index) {
+  this->set_trigger_->trigger(std::string(this->option_at(index)));
 
   if (this->optimistic_)
-    this->publish_state(value);
+    this->publish_state(index);
 
-  if (this->restore_value_) {
-    auto index = this->index_of(value);
-    this->pref_.save(&index.value());
-  }
+  if (this->restore_value_)
+    this->pref_.save(&index);
 }
 
 void TemplateSelect::dump_config() {