Remove TimerEventHandler typedef from Notifier class (#1767)

Using std::function<void()> directly makes it much clearer to the user
what kind of function Notifier expects. The Doxygen comments already say
what the function is used for, so the typedef just discards useful
information.

wpilibc/src/main/native/cpp/Notifier.cpp

@@ -17,7 +17,7 @@
 
 using namespace frc;
 
-Notifier::Notifier(TimerEventHandler handler) {
+Notifier::Notifier(std::function<void()> handler) {
   if (handler == nullptr)
     wpi_setWPIErrorWithContext(NullParameter, "handler must not be nullptr");
   m_handler = handler;
@@ -33,7 +33,7 @@ Notifier::Notifier(TimerEventHandler handler) {
       uint64_t curTime = HAL_WaitForNotifierAlarm(notifier, &status);
       if (curTime == 0 || status != 0) break;
 
-      TimerEventHandler handler;
+      std::function<void()> handler;
       {
         std::scoped_lock lock(m_processMutex);
         handler = m_handler;
@@ -90,7 +90,7 @@ Notifier& Notifier::operator=(Notifier&& rhs) {
   return *this;
 }
 
-void Notifier::SetHandler(TimerEventHandler handler) {
+void Notifier::SetHandler(std::function<void()> handler) {
   std::scoped_lock lock(m_processMutex);
   m_handler = handler;
 }