feat(relay): Re-add {Deposit,Withdrawal,Consolidation}Request objects for relay submissions

[ryanschneider]

Motivation

As reviewing the builder-specs (and unsuccessfully attempting to change them with ethereum/builder-specs#107) I determined that the V4 relay submission actually needs to include the requests in their JSON "object" form rather than the encoded EIP-7865 Vec<Bytes>.

Solution

So, this restores some of the structs removed in #1515 and adds a new RequestsV4 struct to rpc-types-beacon.

A couple things to note:

• In restoring the eip structs I removed the "EL-specific" encoding helpers in favor of the CL flavors (e.g. integers are encoded using DisplayFromStr instead of alloy_serde::quantity. I think this makes sense since these structs are no longer used by the EL/engine API, but I could be convinced to either move these structs in rpc-types-beacon or restore them with "EL-encoding" and add wrapper/custom serde functionality in rpc-types-beacon.
• I also replaced the quantity encoding on SignedBidSubmissionV4::target_blobs_per_block with DisplayFromStr as I'm pretty sure this should be "decimal" encoded.
• The example JSON in crates/rpc-types-beacon/src/examples/relay_builder_block_validation_request_v4.json is a bit of frankenstein, it's a payload I captured from my locally running rbuilder inside our builder-playground with execution_requests and target_blobs_per_block manually edited, but it's the best I could find at the moment.

Note that after this PR is accepted, we'll also need to add functionality for converting eip7865::Requests to rpc-types-beacon::requests::RequestsV4, for use for example flashbots/rbuilder#267. So this PR is only the first step in fully closing #1763

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[ryanschneider]

Closing in favor of #1787 which is a cleaned up version of this that also includes the necessary conversions.