Integrate ExecutedBlock in BuiltPayload

[mattsse]

I would be beneficial to also retrieve the ExecutedBlock from a resolved payload so that we can immediately insert this into the tree ref #10158

this can be achieved by extending the trait for the BuiltPayload:

reth/crates/payload/primitives/src/traits.rs

Line 17 in 4107df8

pub trait BuiltPayload: Send + Sync + std::fmt::Debug {

so that it returns an Option for ExecutedBlock, this should be an option because the payload builder can be anywhere (e.g. a different process)

the main loop can then subscribe to resolved payloads via:

reth/crates/payload/builder/src/service.rs

Lines 228 to 229 in 4107df8

	/// Payload events handler, used to broadcast and subscribe to payload events.
	payload_events: broadcast::Sender<Events<Engine>>,

reth/crates/payload/builder/src/events.rs

Lines 14 to 17 in 4107df8

	/// The built payload that has been just built.
	/// Triggered by the CL whenever it asks for an execution payload.
	/// This event is only thrown if the CL is a validator.
	BuiltPayload(Engine::BuiltPayload),

and if it has an ExecutedBlock we can insert this directly into the tree (#10158)

TODO

1. introduce the Option as trait function
2. change

   reth/crates/ethereum/engine-primitives/src/payload.rs

   Line 28 in 4107df8

   pub struct EthBuiltPayload {

   and

   reth/crates/optimism/payload/src/payload.rs

   Line 166 in 4107df8

   pub struct OptimismBuiltPayload {

   so that they also keep ExecutedBlock
3. integrate in main loop