TimeCheck: Update code to support a callback

Callback will be used for binder statistics and logging.
Nest TimeCheck into mediautils namespace.
Copy input char * to a persistent string.
Log the thread id which is blocked to the debug message.
Separate code to a const shared ptr handler for easier analysis.
Add timecheck_tests which validate callback.

Test: atest libmediautils_test
Test: atest timecheck_tests
Bug: 219958414
Change-Id: I13c751ed90f39e41d7cfa3b8be51e40403787608
diff --git a/media/utils/TimerThread.cpp b/media/utils/TimerThread.cpp
index 3c95798..dfc84e1 100644
--- a/media/utils/TimerThread.cpp
+++ b/media/utils/TimerThread.cpp
@@ -50,9 +50,12 @@
     return deadline;
 }
 
-void TimerThread::cancelTask(Handle handle) {
+// Returns true if cancelled, false if handle doesn't exist.
+// Beware of lock inversion with cancelTask() as the callback
+// is called while holding mMutex.
+bool TimerThread::cancelTask(Handle handle) {
     std::lock_guard _l(mMutex);
-    mMonitorRequests.erase(handle);
+    return mMonitorRequests.erase(handle) != 0;
 }
 
 void TimerThread::threadFunc() {