feat: implement electra deposits

[LeanSerra]

Motivation

Implement changes in Electra to deposits + fix all spec-tests related to it.

Description

• New is_valid_deposit_signature link
• Modified get_validator_from_deposit link
• Modified add_validator_to_registry link
  • In our code the function is called Mutators.apply_initial_deposit
  • The code from Deneb to Electra does not actually change, the link in the spec just adds a comment referencing the changes made to the function get_validator_from_deposit
• Modified apply_deposit link
• New apply_pending_deposit link
• New process_pending_deposits link
• Modified process_operations link
• Modified process_deposit link
  • The code from Deneb to Electra does not actually change, the link in the spec just adds a comment referencing the changes made to the function apply_deposit
• New process_deposit_request link

Fixed Spec Tests

test/generated/mainnet/electra/epoch_processing.exs:
previous: 141 tests, 58 failures
now: 141 tests, 13 failures

test/generated/mainnet/electra/operations.exs
previous: 333 tests, 67 failures
now: 333 tests, 23 failures

test/generated/mainnet/electra/random.exs
previous: 16 tests, 16 failures
now: 16 tests, 3 failures

test/generated/mainnet/electra/sanity.exs
previous: 97 tests, 29 failures, 1 skipped
now: 97 tests, 10 failures, 1 skipped

test/generated/minimal/electra/epoch_processing.exs
previous: 156 tests, 59 failures
now: 156 tests, 13 failures

test/generated/minimal/electra/operations.exs
previous: 366 tests, 104 failures
now: 366 tests, 45 failures

test/generated/minimal/electra/random.exs
previous: 16 tests, 16 failures
now: 16 tests, 2 failures

test/generated/minimal/electra/sanity.exs
previous: 104 tests, 31 failures, 1 skipped
now: 104 tests, 12 failures, 1 skipped

tests fixed: 259

Spec test progress

11370 tests, 165 failures, 784 skipped

[rodrigo-o]

The PR looks good so far, but it's taking me some time to review and try to make some of the functions more clear, so I will leave a batch of comments here and continue with the rest

[rodrigo-o]

LGTM apart from the readability comments. Regarding process_pending_deposits we should probably take some time in the future to refactor it and make it more readable but it requires more effort than the suggested alternatives for the other functions.

BTW we went from 424 (in my latest run in electra-support) to 165 failed tests here, so probably a small summary (num of test x suite) that now pass would be useful in the description of the PR.