Default timer copy constructor causing weird issues

e.g.

```
String s;
s += timer;
```

Doesn't behave as expected and instead constructs new instance then calls destructor on it.
Manifests by hanging HostTests on esp32 (standard, s2 and c3 variants) but curiously not on esp8266 or host.

Sming/Core/CallbackTimer.h

@@ -33,6 +33,12 @@ template <typename ApiDef> struct CallbackTimerApi {
 		return ApiDef::typeName();
 	}
 
+	CallbackTimerApi()
+	{
+	}
+
+	CallbackTimerApi(const CallbackTimerApi&) = delete;
+
 	String name() const
 	{
 		String s;
@@ -50,7 +56,6 @@ template <typename ApiDef> struct CallbackTimerApi {
 		s += static_cast<const ApiDef*>(this)->getInterval();
 		s += ", ticks = ";
 		s += static_cast<const ApiDef*>(this)->ticks();
-		//		s += ApiDef::Clock::ticks();
 		return s;
 	}
 

tests/HostTests/modules/Timers.cpp

@@ -81,7 +81,7 @@ class CallbackTimerTest : public TestGroup
 			String s;
 			s += system_get_time();
 			s += " ";
-			s += statusTimer;
+			s += String(statusTimer);
 			s += " fired, timercount = ";
 			s += activeTimerCount;
 			s += ", mem = ";