This commit moves xTaskIncrementTickOtherCores() to freertos_tasks_c_additions.h
and freertos_idf_additions_priv.h (as API is private). This reduces the code
differences cmpared to upstream FreeRTOS.
This commit refactors port_systick.c so that all ports (RISC-V vs Xtensa) of
all FreeRTOS implementations (IDF vs Amazon SMP FreeRTOS) use the same set of
tick interrupt functions. Thus, these funcitons are now common:
- vPortSetupTimer() to setup the tick interrupt's timer
- xPortSysTickHandler() that is called on each tick interrupt