EIP-7251 open questions / tasks

[ralexstokes]

• Reconsider use of effective balances in computing consolidation (and likely also exit) churn, as the limits are also a function of effective balance and it seems to prevent the possibility of having multiple validators exit each epoch. see here for an example where going one unit past the churn limit does not move to the next epoch
• Reconsider how the "partial withdrawals processed" counter in get_expected_withdrawals works as it is backwards incompatible with that function's signature in previous forks. It is possible we could do something like pop on the pending_partial_withdrawals list, although also see this
• Revisit how deposits are handled between pre-EIP-7251 and post-EIP-7251 (cf. #3656)
• #3670
• #3661
• #3659
• #3650
• #3677
• Handle TODO to update light client g-indices #3668 (comment)
• Revisit balance processing and exit epoch calculation #3668 (comment)
• Add EIP-7251 validator guide
• Add EIP-7251 new gossip topics
• Consider consolidating the logic across the two functions touched in this PR: #3682 and add a test case for the underlying issue #3677

Tests to write

Test this: #3679
Revisit this test: #3681 (comment), may just need to manually check "is partially withdrawable", like we do in some other tests