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/common/runtime.hpp

@@ -0,0 +1,54 @@
+#ifndef RUNTIME_HPP_KHDIEMRN
+#define RUNTIME_HPP_KHDIEMRN
+
+#include <vanetza/common/clock.hpp>
+#include <functional>
+
+namespace vanetza
+{
+
+/**
+ * Runtime provides current time and enables scheduling of tasks for later execution.
+ *
+ * All calls to Runtime and objects using the same Runtime have to be invoked from same thread!
+ **/
+class Runtime
+{
+public:
+    using Callback = std::function<void(Clock::time_point)>;
+
+    /**
+     * Schedule callback for later invocation
+     * \param tp invoke callback at this time point
+     * \param cb callback
+     * \param scope associated scope pointer (used only for identification)
+     */
+    virtual void schedule(Clock::time_point tp, const Callback& cb, const void* scope = nullptr) = 0;
+
+    /**
+     * Schedule callback for later invocation
+     * \param d duration from now until callback invocation
+     * \param cb callback
+     * \param scope associated scope pointer (used only for identification)
+     */
+    virtual void schedule(Clock::duration d, const Callback& cb, const void* scope = nullptr) = 0;
+
+    /**
+     * Cancel all scheduled invocations assigned to certain scope
+     * \param scope any pointer used as scope at scheduling (nullptr has no effect)
+     */
+    virtual void cancel(const void* scope) = 0;
+
+    /**
+     * Get current time
+     * \return current time
+     */
+    virtual Clock::time_point now() const = 0;
+
+    virtual ~Runtime() = default;
+};
+
+} // namespace vanetza
+
+#endif /* RUNTIME_HPP_KHDIEMRN */
+