This PR implements the contract API to query the code size of a given
address.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Signed-off-by: xermicus <cyrill@parity.io>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: command-bot <>
Co-authored-by: PG Herveou <pgherveou@gmail.com>