Strict fee recipient (#3363)

## Issue Addressed

Resolves #3267
Resolves #3156 

## Proposed Changes

- Move the log for fee recipient checks from proposer cache insertion into block proposal so we are directly checking what we get from the EE
- Only log when there is a discrepancy with the local EE, not when using the builder API. In the `builder-api` branch there is an `info` log when there is a discrepancy, I think it is more likely there will be a difference in fee recipient with the builder api because proposer payments might be made via a transaction in the block. Not really sure what patterns will become commong.
- Upgrade the log from a `warn` to an `error` - not actually sure which we want, but I think this is worth an error because the local EE with default transaction ordering I think should pretty much always use the provided fee recipient
- add a `strict-fee-recipient` flag to the VC so we only sign blocks with matching fee recipients. Falls back from the builder API to the local API if there is a discrepancy .




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

validator_client/src/config.rs

@@ -56,6 +56,9 @@ pub struct Config {
     /// A list of custom certificates that the validator client will additionally use when
     /// connecting to a beacon node over SSL/TLS.
     pub beacon_nodes_tls_certs: Option<Vec<PathBuf>>,
+    /// Enabling this will make sure the validator client never signs a block whose `fee_recipient`
+    /// does not match the `suggested_fee_recipient`.
+    pub strict_fee_recipient: bool,
 }
 
 impl Default for Config {
@@ -89,6 +92,7 @@ impl Default for Config {
             enable_doppelganger_protection: false,
             beacon_nodes_tls_certs: None,
             private_tx_proposals: false,
+            strict_fee_recipient: false,
         }
     }
 }
@@ -300,6 +304,10 @@ impl Config {
             config.private_tx_proposals = true;
         }
 
+        if cli_args.is_present("strict-fee-recipient") {
+            config.strict_fee_recipient = true;
+        }
+
         Ok(config)
     }
 }