This commit updates the ESP-IDF FreeRTOS and FreeRTOS Additions to account for
the fact that there are now two implementations of SMP FreeRTOS (i.e., IDF SMP
vs Amazon SMP).
This commit renames "freertos-smp" docuemnt to "freertos_idf". This fits better
with the current dual FreeRTOS implementation (i.e., IDF FreeRTOS and Amazon
SMP FreeRTOS), both of which are SMP capable.
Darian Leung