gloas vc block production

[shane-moore]

Changes

• added VC side block production flow for gloas to support self-building for the devnet-0 release, per spec

How This Works

In Gloas, the publish_block flow in the VC is modified to add the get, sign, and publish of a payload envelope, which occus when the BeaconBlock.body.signed_execution_payload_bid.message.builder_index is the same as the proposer's validator index.

Additionally, when requesting a block from the BN, we will no longer receive blobs or kzg commitments. Instead, payload envelopes and blobs will be released by the proposer in the self-building scenario or otherwise by the in-protocol builder. There is no longer a concept of requesting unblinded or blinded blocks since all CL blocks just contain bids.

Client-side endpoints were added to support requesting gloas block and additionally envelopes. All the new and modified epbs beacon api endpoints are defined in PR.

Todo's (left comments in the code as well)

• the server side (BN) response to the api's modified and added in this PR will need to be handled since we're only touching the VC in this PR. This is contingent on the upcoming envelope_verification.rs flow since we request an envelope to sign and gossip during block production. Additionally, the produce_block call to the BN will no longer respond with blobs for example, so we'll need to modify this endpoint. Additionally, the BN endpoint that receives the signed block to broadcast flow will need to be modified as well.
• add tests for produce_block_v4 and other new endpoints on the server side