BN Fallback v2 (#2080)

## Issue Addressed

- Resolves #1883

## Proposed Changes

This follows on from @blacktemplar's work in #2018.

- Allows the VC to connect to multiple BN for redundancy.
  - Update the simulator so some nodes always need to rely on their fallback.
- Adds some extra deprecation warnings for `--eth1-endpoint`
- Pass `SignatureBytes` as a reference instead of by value.

## Additional Info

NA

Co-authored-by: blacktemplar <blacktemplar@a1.net>

beacon_node/http_api/tests/tests.rs

@@ -1643,7 +1643,7 @@ impl ApiTester {
 
             let block = self
                 .client
-                .get_validator_blocks::<E>(slot, randao_reveal, None)
+                .get_validator_blocks::<E>(slot, &randao_reveal, None)
                 .await
                 .unwrap()
                 .data;