Change getPayload timeout to 2s

[lucassaldanha]

PR Description

Update the default timeout of getPayload to 2s. In our testing, that was enough to increase the successful requests even under stress scenarios (e.g. higher blob count).

At this moment, I am not adding a CLI flag to configure this. I'll plan something for the new Engine API client that will be introduced soon.

Fixed Issue(s)

N/A

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.

---

Note

Low Risk
Small, isolated timeout change for a specific set of RPC calls; main risk is slightly longer waits before failing when the execution client is unresponsive.

Overview
Increases the default timeout used for Engine API engine_getPayloadV1–engine_getPayloadV6 calls in Web3JExecutionEngineClient from the shared EL_ENGINE_NON_BLOCK_EXECUTION_TIMEOUT (1s) to a dedicated 2-second GET_PAYLOAD_TIMEOUT.

Adds a matching CHANGELOG.md entry documenting the new default timeout for Get Payload requests.

^{Written by Cursor Bugbot for commit 2e4086c. This will update automatically on new commits. Configure here.}