Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/tools/socktap/benchmark_application.cpp

@@ -0,0 +1,52 @@
+#include "benchmark_application.hpp"
+#include <chrono>
+#include <iostream>
+
+// Benchmark application counts all incoming messages and calculates the message rate.
+
+using namespace std::chrono;
+using namespace vanetza;
+
+BenchmarkApplication::BenchmarkApplication(boost::asio::io_context& io) :
+    m_timer(io), m_interval(std::chrono::seconds(1))
+{
+    schedule_timer();
+}
+
+BenchmarkApplication::PortType BenchmarkApplication::port()
+{
+    return host_cast<uint16_t>(0);
+}
+
+Application::PromiscuousHook* BenchmarkApplication::promiscuous_hook()
+{
+    return this;
+}
+
+void BenchmarkApplication::tap_packet(const DataIndication&, const UpPacket&)
+{
+    ++m_received_messages;
+}
+
+void BenchmarkApplication::indicate(const DataIndication&, UpPacketPtr)
+{
+    // do nothing here
+}
+
+void BenchmarkApplication::schedule_timer()
+{
+    m_timer.expires_after(m_interval);
+    m_timer.async_wait(std::bind(&BenchmarkApplication::on_timer, this, std::placeholders::_1));
+}
+
+void BenchmarkApplication::on_timer(const boost::system::error_code& ec)
+{
+    if (ec == boost::asio::error::operation_aborted) {
+        return;
+    }
+
+    std::cout << "Received " << m_received_messages << " messages/second" << std::endl;
+    m_received_messages = 0;
+
+    schedule_timer();
+}