stmhal: Update ADC, DAC and I2C objects to use new buffer protocol.
Main reason for expanding buffer protocol API was to support writes to a buffer in ADC module (see read_timed). With this change you can now create an array of arbitrary type and ADC.read_timed will store into that array in the correct format (byte, int, float). I wonder though if all these changes were really worth it to support just this function. Hopefully this enhanced buffer protocol API (with typecode specified) will be used elsewhere.