implement engine get exeuction payload bodies v2

[mehdi-aouadi]

PR Description

Implement engine_getPayloadBodiesByHashV2 required for execution payload unblinding

Fixed Issue(s)

partially #10098

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

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Note

Medium Risk
Adds a new Engine API call and wires it through execution client, execution layer handler, and capability negotiation; incorrect wiring/serialization could break payload unblinding flows or EL compatibility for Gloas+ networks.

Overview
Adds support for the EL JSON-RPC method engine_getPayloadBodiesByHashV2 end-to-end to enable execution payload unblinding.

This introduces the ExecutionPayloadBodyV2 execution-client schema plus a new internal ExecutionPayloadBody type, exposes a new ExecutionEngineClient.getPayloadBodiesByHashV2 call (with throttling, metrics, and web3j implementations), and adds a corresponding engine JSON-RPC method wrapper EngineGetPayloadBodiesByHashV2.

The execution layer is extended with engineGetPayloadBodiesByHash plumbing (handler + manager) and the milestone resolver advertises/serves the method for GLOAS (and later) capabilities; integration and resolver tests are updated to cover request/response round-tripping and capability listing.

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[tbenr]

LGTM