Renames exits to withdraw requests all over the code

[mkalinin]

Depends on #7, decided to put this change aside as renaming is quite big in terms of the diff.

EIP-7002 is extended to support not only full exits but also partial withdrawals, thus, exit should be replaced with a more general term. Withdraw requests is the term used by the EIP-7251 CL spec.

[ralexstokes]

given that we are multiplexing multiple operations on top of the one EL message, it may be better to use an even more general term like OperationRequest

esp if we end up with 7251 EL-init'd consolidation messages, this may end up a bit overloaded so a more general name is better

[mkalinin]

given that we are multiplexing multiple operations on top of the one EL message, it may be better to use an even more general term like OperationRequest

esp if we end up with 7251 EL-init'd consolidation messages, this may end up a bit overloaded so a more general name is better

I don’t think we will have any other EL activated operation as a part of 7002. If we end up introducing EL triggered consolidations or anything else after 7002 this will rather be another EIP with its own terms and data structs.