This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.
This commit removes the usage of all legacy FreeRTOS data types that
are exposed via configENABLE_BACKWARD_COMPATIBILITY. Legacy types can
still be used by enabling CONFIG_FREERTOS_ENABLE_BACKWARD_COMPATIBILITY.
By using IOMUX instead of GPIO Matrix for UART, it is now possible
on ESP32 boards to use the UART as a wake up source even if it is
not used as a console.
For other boards where this issue was not present, using IOMUX has
the advantage to be faster than using GPIO matrix, so a highest
baudrate can be used
