[core] Move heap-allocating helpers to alloc_helpers.h/cpp (#15623)

esphome/components/http_request/http_request.cpp

@@ -22,7 +22,7 @@ void HttpRequestComponent::dump_config() {
 }
 
 std::string HttpContainer::get_response_header(const std::string &header_name) {
-  auto lower = str_lower_case(header_name);
+  auto lower = str_lower_case(header_name);  // NOLINT
   for (const auto &entry : this->response_headers_) {
     if (entry.name == lower) {
       ESP_LOGD(TAG, "Header with name %s found with value %s", lower.c_str(), entry.value.c_str());