Kiln mev boost (#3062)

## Issue Addressed

MEV boost compatibility

## Proposed Changes

See #2987

## Additional Info

This is blocked on the stabilization of a couple specs, [here](https://github.com/ethereum/beacon-APIs/pull/194) and [here](https://github.com/flashbots/mev-boost/pull/20).

Additional TODO's and outstanding questions

- [ ] MEV boost JWT Auth
- [ ] Will `builder_proposeBlindedBlock` return the revealed payload for the BN to propogate
- [ ] Should we remove `private-tx-proposals` flag and communicate BN <> VC with blinded blocks by default once these endpoints enter the beacon-API's repo? This simplifies merge transition logic. 

Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: realbigsean <sean@sigmaprime.io>

beacon_node/beacon_chain/tests/block_verification.rs

@@ -12,6 +12,7 @@ use state_processing::{
     per_block_processing::{per_block_processing, BlockSignatureStrategy},
     per_slot_processing, BlockProcessingError, VerifyBlockRoot,
 };
+use std::marker::PhantomData;
 use std::sync::Arc;
 use tempfile::tempdir;
 use types::{test_utils::generate_deterministic_keypair, *};
@@ -962,6 +963,7 @@ fn add_base_block_to_altair_chain() {
                 attestations: altair_body.attestations.clone(),
                 deposits: altair_body.deposits.clone(),
                 voluntary_exits: altair_body.voluntary_exits.clone(),
+                _phantom: PhantomData,
             },
         },
         signature: Signature::empty(),
@@ -1082,6 +1084,7 @@ fn add_altair_block_to_base_chain() {
                 deposits: base_body.deposits.clone(),
                 voluntary_exits: base_body.voluntary_exits.clone(),
                 sync_aggregate: SyncAggregate::empty(),
+                _phantom: PhantomData,
             },
         },
         signature: Signature::empty(),