samples/shields: add samples to test x-nucleo-iks02a1 shield

Provide three basic examples to test the x-nucleo-iks02a1 shield:

    - Test shield standard mode
        Acquire sensor data from shield configured in mode 1.

    - Test shield sensorhub mode
        Acquire sensor data from shield configured in mode 2.

    - Test on-shield microphone
        Acquire microphone PDM audio and output it in 16-bit
        PCM format to console.

Signed-off-by: Armando Visconti <armando.visconti@st.com>
17 files changed