add a Lock, LockGuard and printThreadInfo

* `Lock`: trivial wrapper for FreeRTOS binary semaphores
* `LockGuard`: RAII wrapper for using `Lock`
* `printThreadInfo`: helper for showing which core/FreeRTOS task we are
  running under

src/debug.cpp

@@ -0,0 +1,20 @@
+#include "debug.h"
+
+#include <cstdint>
+
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+
+#include "configuration.h"
+
+namespace meshtastic
+{
+
+void printThreadInfo(const char *extra)
+{
+    uint32_t taskHandle = reinterpret_cast<uint32_t>(xTaskGetCurrentTaskHandle());
+    DEBUG_MSG("printThreadInfo(%s) task: %" PRIx32 " core id: %u min free stack: %u\n", extra, taskHandle, xPortGetCoreID(),
+              uxTaskGetStackHighWaterMark(nullptr));
+}
+
+} // namespace meshtastic