Liquid solo validating

To repeat what I said here: Withdrawal Credentials Exits Based On A Generalized Message Bus - #7 by A1igator

Some form of liquid staking for solo validators is needed to keep them competitive with leveraged staking. The proposal above is obviously not ideal due to trust assumptions of Intel SGX but I’m glad EF is heading to this direction.

@MicahZoltu rightfully does point out that this reduces the cost of attack so I think that’s good to keep in mind as well.