Followup tracker for MeV related pending issues/cleanup

[g11tech]

This is a followup tracker for the

• https://github.com/ChainSafe/lodestar/pull/3969

Tasks

• [ ] add the blinded variants to getForkTypes
• [ ] [blinded vs full block strategy] (https://github.com/ChainSafe/lodestar/pull/3969#discussion_r898818937)
• [ ] mergemock builder integration tests
• [x] Add metrics
• [ ] Validate the signature in signed builder bid received and validate for amount > min block rewards
• [x] https://github.com/ChainSafe/lodestar/pull/4488
• [x] 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
  •