fix: flashblock benchmark scheduling

[meyer9]

Description

• Synchronize flashblock sending with full block sending so we're sending the flashblocks for block N immediately after NewPayload is acknowledged for block N-1 via startedBlockSignal
• Include last setup block in payloads so that we can start sending flashblocks immediately after the last setup block is processed (still don't collect metrics for this block though)
• Group flashblocks by block during collection instead of during replay since only the first flashblock includes the base block info
• Sleep for block time during validation (previously were calling NewPayload as fast as possible)

Testing

Tested with rbuilder and base-node-reth

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[meyer9]

previously, validator benchmark wasn't sleeping (also caused an issue with Reth processing spikes)

[cb-heimdall]

Review Error for mw2000 @ 2026-01-22 19:58:30 UTC
User failed mfa authentication, see go/mfa-help

Approved review 3694865793 from mw2000 is now dismissed due to new commit. Re-request for approval.