[Blinky] Convert FreeRTOS calls into CMSIS RTOS.

- Refactor main.c file to use CMSIS RTOS and GPIO HAL API
- Add FreeRTOS heap definition to application_helpers.c - common for both apps
- Remove FreeRTOS adaptation file.
- Move FreeRTOS configuration file to the common directory.

Signed-off-by: Vincent Coubard <vincent.coubard@arm.com>