freertos port for stm32f429zi

[Ivanca21]

This PR adds initial FreeRTOS support for STM32F429ZI in mikroSDK v2.

Changes:

• Added thirdparty/FreeRTOS/FreeRTOS-Kernel.
• Introduced a new CMake library MikroSDK.FreeRTOSKernel that:
  • builds core kernel sources (tasks.c, queue.c, timers.c, event_groups.c, stream_buffer.c, list.c)
  • uses the portable/GCC/ARM_CM4F port
  • uses portable/MemMang/heap_4.c as the default heap implementation.
• Added target–specific configuration file
  targets/arm/mikroe/common/include/FreeRTOSConfig/STM32/STM32F429ZI/FreeRTOSConfig.h.
• Hooked FreeRTOS into the build only for:
  • TOOLCHAIN_ID = gcc_arm_none_eabi
  • MCU_NAME = STM32F429ZI
    via thirdparty/CMakeLists.txt and tests/CMakeLists.txt.

New tests:

• Added tests/freertos/ group with the following examples:
  • task_test – basic LED blink task
  • task_notification
  • sw_timer
  • queue
  • mutex
  • event_group
  • counting_semaphore
  • binary_semaphore

Notes:

• No changes were made to existing HAL/DRV implementations.
• FreeRTOS is currently enabled only for STM32F429ZI + GCC; other MCUs/toolchains are unaffected.
• Directory structure is prepared so that additional MCUs can be added later by:
  • providing a new FreeRTOSConfig.h under targets/.../FreeRTOSConfig/...
  • extending the CMake logic in thirdparty/FreeRTOS and tests/freertos.