feat(engine): Block building task

[clabby]

Overview

Adds a new task to the EngineTasks that builds a new block with engine_forkchoiceUpdate and then imports it with engine_newPayload. As a side effect, it updates the local heads after the payload imports successfully.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 91.5%. Comparing base (2c9fa5e) to head (bc61cb8).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/node/rpc/src/attributes.rs	0.0%	6 Missing ⚠️

Additional details and impacted files

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