Test: Add a test for processing multiple deposits within the same epoch for a given validator

[bshastry]

Issue Addressed

ethereum/consensus-specs#4021

Proposed Changes

The idea is to create pre/post electra tests that do the following

• create a deposit in block N, epoch E for validator X
• create another deposit in block N + 3, epoch E for validator X
• assert that the balance of the validator after processing the deposits in the epoch equals expectation

Additional Info

The test case pre electra works. I have not been able to correctly model state transition to electra (this test currently panics due to the mock execution layer not being able to provide a valid payload), so help there would be appreciated. I have hence maked this PR, draft.

[CLAassistant]

All committers have signed the CLA.

[bshastry]

This PR is waiting on CI workflow approval I think

[bshastry]

The test case for Electra fails because I don't know how to process deposit requests, can you please guide me?

per_block_processing::tests::test_multiple_deposits_same_validator_same_epoch_post_electra ---
thread 'per_block_processing::tests::test_multiple_deposits_same_validator_same_epoch_post_electra' panicked at consensus/state_processing/src/per_block_processing/tests.rs:1322:5:
Found the following validation errors:
Validator 1 balance is 32001788855 gwei, expected 34001788855 gwei (initial: 32001788855 + deposits: 2000000000)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace