feat: implement new beacon APIs(accessors for pending_deposits/pending_partial_withdrawals)

[syjn99]

Issue Addressed

Resolves #7003

Proposed Changes

Added two endpoints as ethereum/beacon-APIs#500 proposed:

• /eth/v1/beacon/states/{state_id}/pending_deposits
• /eth/v1/beacon/states/{state_id}/pending_partial_withdrawals

Additional Info

#7005 breaks current test set-up right now. #7007 fixes the issue, but not yet merged to unstable branch.

[michaelsproul]

Looks good at a glance, you're definitely on the right track. I've triggered CI so you can see if the tests pass. You can also run locally, just not in debug mode

[michaelsproul]

You can fix the cargo format failure by running cargo fmt --all

[syjn99]

RUST_MIN_STACK=16777216 cargo test beacon_get_state_info_electra -p http_api --test bn_http_api_tests -- --nocapture

@michaelsproul Hi, thanks to #7007, I found that my test successfully passed with the commit. However, I'm afraid that default BeaconChainHarness will always return empty list of pending_deposits/pending_partial_withdrawals as it is initialized with default value. Do I have to add a case for comparing not emptied list? If then, would you mind letting me know where the good place to start?