simulators/eth2/withdrawals: add builder tests

[marioevz]

Changes Included

• Adds a mock builder to the eth2/common library that is able to relay payload requests to a local Execution client to simulate a working builder
  • Client receives and registers validators to produce payloads when requested
  • When requested, the builder queries the CL for its state to obtain the prevrandao value to be able to construct the correct payload attributes
  • The payload attributes are relayed to the EL and then it waits for the payload to be built
  • The builder constructs and signs a builder bid which is returned to the CL
  • When the signed blinded beacon block is received, the full payload (transactions + withdrawals) is sent as response
• Changes all Beacon clients to include builder parameters

Clients passing tests:

• Nimbus
• Lighthouse
• Prysm
• Teku
• Lodestar

Lodestar test is currently failing because it stops requesting headers from the builder at the Capella fork. Fixed by ChainSafe/lodestar#5179

[marioevz]

@fjl let me know if it's ok to include client's changes in this same PR or I can split it up in a PR for each client (adds Builder API parameters to all consensus clients).