freertos: don't create timer task if timer APIs are not used

Saves 2496 bytes of heap for the hello-world app on the ESP32,
and 4080 bytes of heap on the ESP32-S2 (due to IRAM savings).

components/freertos/tasks.c

@@ -5137,3 +5137,8 @@ TickType_t uxReturn;
 	#include "tasks_test_access_functions.h"
 #endif
 
+/* If timers.c is not referenced anywhere, don't create the timer task to save RAM */
+BaseType_t  __attribute__((weak)) xTimerCreateTimerTask( void )
+{
+	return pdPASS;
+}