Add support for the Kintsugi network

[remyroy]

It would be nice to add support for the Kintsugi network. The testnet details are in https://github.com/eth-clients/merge-testnets/tree/main/kintsugi . It seems like @avsetsin started working on it in https://github.com/lidofinance/eth2.0-deposit-cli/tree/kintsugi but I don't know where it's at now.

[remyroy]

It might not be worth adding support for Kintsugi. Here is a comment from Danny Ryan on its lifespan.

Kintsugi will be dropped in favor of a reboot on the order of two weeks from now
assuming no further changse, this reboot would likely run through the merge

Maybe that next merge testnet could be supported by eth2.0-deposit-cli.

[djrtwo]

I think the next testnet is a good target. we'll be encouraging more and more users to try it out

[CarlBeek]

Kintsugi (and Kiln) support added via #240. Thanks regardless @remyroy!