arm: async changes

- more tracing
- pending resume() notifications
- idle function returns bool (useful for testing)

may not build (more stuff coming in later commits)

arm/trace.h

@@ -1,14 +1,48 @@
 #pragma once
 
+#define TRACE_DUMP_WHEN_FULL 0
+
+#ifdef __x86_64__
+#include <cstdio>
+#define TRACE(x) printf(#x "\n")
+#else  // __x86_64__
+#define TRACE(...) tracing::trace(__VA_ARGS__)
+#endif  // __x86_64__
+
 #include <cstdint>
 
 namespace tracing {
 enum class TraceEvent : uint8_t {
     kUnknown = 0,
 
-    kUartIsr,
-    kUartRxCb,
-    kUartTxCb,
+    kUartIsr = 1,
+    kUartRxCb = 2,
+    kUartTxCb = 3,
+
+    kUartSend = 10,
+    kUartRecv = 11,
+    kUartTxBufferFull = 12,
+    kUartTxBufferNotFull = 13,
+
+    kUartWriteDone = 20,
+
+    kAsyncResume = 4,
+    kAsyncEnqueue = 5,
+    kAsyncTask = 6,
+    kAsyncResumeSetPending = 7,
+    kAsyncAwaitWasNotified = 8,
+    kAsyncSchedule = 9,
+
+    kAsyncTaskDone = 14,
+    kAsyncException = 15,
+    kAsyncCallParent = 16,
+    kAsyncCallParentDone = 17,
+    kAsyncCoAwait = 18,
+    kAsyncSuspend = 19,
+    kAsyncDestroy = 21,
+
+    kAsyncGimmeWaiting = 22,
+    kAsyncGimmeResume = 23,
 };
 
 void trace(TraceEvent event);