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/vanetza/dcc/bursty_transmit_rate_control.hpp

@@ -0,0 +1,43 @@
+#ifndef BURSTY_TRANSMIT_RATE_CONTROL_HPP_AM7LROYD
+#define BURSTY_TRANSMIT_RATE_CONTROL_HPP_AM7LROYD
+
+#include <vanetza/common/clock.hpp>
+#include <vanetza/dcc/burst_budget.hpp>
+#include <vanetza/dcc/profile.hpp>
+#include <vanetza/dcc/state_machine_budget.hpp>
+#include <vanetza/dcc/transmit_rate_control.hpp>
+
+namespace vanetza
+{
+
+// forward declarations
+class Runtime;
+namespace dcc { class StateMachine; }
+
+namespace dcc
+{
+
+/**
+ * Transmit Rate Control with occasional DP0 message bursts.
+ * DP1, DP2 and DP3 messages are controlled by a state machine only.
+ */
+class BurstyTransmitRateControl : public TransmitRateControl
+{
+public:
+    BurstyTransmitRateControl(const StateMachine&, const Runtime& rt);
+
+    Clock::duration delay(const Transmission&) override;
+    Clock::duration interval(const Transmission&) override;
+    void notify(const Transmission&) override;
+
+private:
+    BurstBudget m_burst_budget;
+    StateMachineBudget m_fsm_budget;
+    const StateMachine& m_fsm;
+};
+
+} // namespace dcc
+} // namespace vanetza
+
+#endif /* BURSTY_TRANSMIT_RATE_CONTROL_HPP_AM7LROYD */
+