digital_electricity: use 7 segment display in level 22

Level 22: The output of the BCD counter is displayed on the seven
segment display via the BCD to seven segment component.

Answer is checked by comparing the values of the BCD counter and that of
the BCD to seven segment display and by checking if all of the terminals
of the components are connected (they may both be = 0 if not connected)

Signed-off-by: Rudra Nil Basu <rudra.nil.basu.1996@gmail.com>