This commit updates task snapshot as follows:
- Refactored implementation to increase readability
- Implementation moved into freertos_tasks_c_additions.h
- freertos_tasks_c_additions.h made a private header
- Support SMP FreeRTOS
- Removed configENABLE_TASK_SNAPSHOT option. CONFIG_FREERTOS_ENABLE_TASK_SNAPSHOT
is direclty used instead.