Add function to shuffle an entire list instead of one element at a time

[mpaulucci]

See this comment by lighthouse:

https://github.com/sigp/lighthouse/blob/441fc1691b69f9edc4bbdc6665f3efab16265c9b/consensus/swap_or_not_shuffle/src/shuffle_list.rs#L52-L78C1

We should also have something like this.

[h3lio5]

can I take this one?

[MegaRedHand]

Hey @h3lio5 ! Sorry, but I'm gonna take this issue. As part of the optimizations I'm working on, I'll implement this and check if it reduces the amount of processing in process_attestation