Proposal: add validator registration into the transcript

[metachris]

I think the transcript should include the validator registration.

• It would remove the need to handle all of the registrations every epoch, quite unnecessarily.
  • This is a major pain point on the mev-boost relays, because 400k registrations come in all at once and need to be validated in time. Removing the need to handle these will make it significantly easier to run relay monitor, and also reduces the bandwidth requirements for both proposers and monitor operators.
  • Leaking all validator registrations is also a privacy concern (see also https://collective.flashbots.net/t/privacy-concerns-with-data-api/568)
• if the transcript contains the validator registration, it contains all the available information, and doesn't rely on correlation with any other requests or collected data