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>

lighthouse/tests/validator_client.rs

@@ -388,3 +388,16 @@ fn no_doppelganger_protection_flag() {
         .run()
         .with_config(|config| assert!(!config.enable_doppelganger_protection));
 }
+#[test]
+fn strict_fee_recipient_flag() {
+    CommandLineTest::new()
+        .flag("strict-fee-recipient", None)
+        .run()
+        .with_config(|config| assert!(config.strict_fee_recipient));
+}
+#[test]
+fn no_strict_fee_recipient_flag() {
+    CommandLineTest::new()
+        .run()
+        .with_config(|config| assert!(!config.strict_fee_recipient));
+}