Followup tracker for MeV related pending issues/cleanup

[g11tech]

This is a followup tracker for the

• Mev/Builder api integration #3969

Tasks

• add the blinded variants to getForkTypes
• [blinded vs full block strategy] (Mev/Builder api integration #3969 (comment))
• Setup mergemock based builder tests #4703
• Add metrics
  - [ ] Validate the signature in signed builder bid received and validate for amount > min block rewards
• Add circuit breaker for builder #4488
• Do not create a new validator registration data unless change in reg data
  • this has been requested by the mev boost team to avoid load on relays, still send registrations but don't create new ones
  •