Remove builder redundancy (#3294)

## Issue Addressed

This PR is a subset of the changes in #3134. Unstable will still not function correctly with the new builder spec once this is merged, #3134 should be used on testnets

## Proposed Changes

- Removes redundancy in "builders" (servers implementing the builder spec)
- Renames `payload-builder` flag to `builder`
- Moves from old builder RPC API to new HTTP API, but does not implement the validator registration API (implemented in https://github.com/sigp/lighthouse/pull/3194)



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

consensus/types/src/builder_bid.rs

@@ -0,0 +1,52 @@
+use crate::{EthSpec, ExecPayload, ExecutionPayloadHeader, Uint256};
+use bls::blst_implementations::PublicKeyBytes;
+use bls::Signature;
+use serde::{Deserialize as De, Deserializer, Serialize as Ser, Serializer};
+use serde_derive::{Deserialize, Serialize};
+use serde_with::{serde_as, DeserializeAs, SerializeAs};
+use std::marker::PhantomData;
+
+#[serde_as]
+#[derive(PartialEq, Debug, Serialize, Deserialize, Clone)]
+#[serde(bound = "E: EthSpec, Payload: ExecPayload<E>")]
+pub struct BuilderBid<E: EthSpec, Payload: ExecPayload<E>> {
+    #[serde_as(as = "BlindedPayloadAsHeader<E>")]
+    pub header: Payload,
+    #[serde(with = "eth2_serde_utils::quoted_u256")]
+    pub value: Uint256,
+    pub pubkey: PublicKeyBytes,
+    #[serde(skip)]
+    _phantom_data: PhantomData<E>,
+}
+
+/// Validator registration, for use in interacting with servers implementing the builder API.
+#[derive(PartialEq, Debug, Serialize, Deserialize, Clone)]
+#[serde(bound = "E: EthSpec, Payload: ExecPayload<E>")]
+pub struct SignedBuilderBid<E: EthSpec, Payload: ExecPayload<E>> {
+    pub message: BuilderBid<E, Payload>,
+    pub signature: Signature,
+}
+
+struct BlindedPayloadAsHeader<E>(PhantomData<E>);
+
+impl<E: EthSpec, Payload: ExecPayload<E>> SerializeAs<Payload> for BlindedPayloadAsHeader<E> {
+    fn serialize_as<S>(source: &Payload, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        source.to_execution_payload_header().serialize(serializer)
+    }
+}
+
+impl<'de, E: EthSpec, Payload: ExecPayload<E>> DeserializeAs<'de, Payload>
+    for BlindedPayloadAsHeader<E>
+{
+    fn deserialize_as<D>(deserializer: D) -> Result<Payload, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let payload_header = ExecutionPayloadHeader::deserialize(deserializer)?;
+        Payload::try_from(payload_header)
+            .map_err(|_| serde::de::Error::custom("unable to convert payload header to payload"))
+    }
+}

consensus/types/src/lib.rs

@@ -28,6 +28,7 @@ pub mod beacon_block_body;
 pub mod beacon_block_header;
 pub mod beacon_committee;
 pub mod beacon_state;
+pub mod builder_bid;
 pub mod chain_spec;
 pub mod checkpoint;
 pub mod consts;