This change implements withdrawals as specified in EIP-4895.
Co-authored-by: lightclient@protonmail.com <lightclient@protonmail.com>
Co-authored-by: marioevz <marioevz@gmail.com>
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>
