tests: drivers: adc: adc_api: update adc_api test

-add nucleo_u083rc and stm32u083c_dk overlays files
for testbench purpose.
- add platform_exclude property to skip test on boards
with little ram size.

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>

tests: drivers: adc: adc_api: update adc_api test