Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/tools/socktap/benchmark_application.hpp

@@ -0,0 +1,27 @@
+#ifndef BENCHMARK_APPLICATION_HPP_EUIC2VFR
+#define BENCHMARK_APPLICATION_HPP_EUIC2VFR
+
+#include "application.hpp"
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <chrono>
+
+class BenchmarkApplication : public Application, private Application::PromiscuousHook
+{
+public:
+    BenchmarkApplication(boost::asio::io_context&);
+    PortType port() override;
+    void indicate(const DataIndication&, UpPacketPtr) override;
+    Application::PromiscuousHook* promiscuous_hook() override;
+
+private:
+    void schedule_timer();
+    void on_timer(const boost::system::error_code& ec);
+    void tap_packet(const DataIndication&, const vanetza::UpPacket&) override;
+
+    boost::asio::steady_timer m_timer;
+    std::chrono::milliseconds m_interval;
+    unsigned m_received_messages;
+};
+
+#endif /* BENCHMARK_APPLICATION_HPP_EUIC2VFR */