boards: arm: stm32f303 nucleo with pyocd and cubeprogrammer as runner

Add the pyocd ant the stm32cubeprogrammer as a runner of the
nucleo_f303k8 platforms,
when the openocd gives an flashing error.
Add the pyocd pack if needed : 'pyocd pack install stm32f303'

Signed-off-by: Francois Ramu <francois.ramu@st.com>