Description

As discovered in #20773 (comment), some variants of the STM32 ADC peripheral use magic numbers in an undocumented way to check if the ADC resolution has a valid value or or not:
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_f0_g0_c0.c#L103-L106
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_f2.c#L112-L114
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_f3.c#L196-L199
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_f4_f7.c#L131-L134
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_l4_wb.c#L220-L223
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_wl.c#L121-L124

Some other implementations explicitly check if the resolution value is one of the valid values, so IMO this is the better approach:
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_f1.c#L146-L149
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_l0.c#L120-L126
https://github.com/RIOT-OS/RIOT/blob/master/cpu/stm32/periph/adc_l1.c#L149-L155

I have the following STM32 boards available:
NUCLEO-F413ZH
NUCLEO-G474RE (not supported yet, seems to have the same ADC as the H7 series and quite similar to L4, just a little more options)
NUCLEO-L073RZ (irrelevant, won't be changed)
NUCLEO-L452RE
P-NUCLEO-WB55 (duplicate for L4)

So we're still missing F0/F0/C0, F2, F3 and WL boards for testing. Maybe I can get some of them from Mouser in the future, but maybe someone else has some of these boards for testing.

Useful links

STM32G474 Reference Manual: https://www.st.com/resource/en/datasheet/stm32g474cb.pdf p.591