Remove consensus/types re-exports (#8540)

There are certain crates which we re-export within `types` which creates a fragmented DevEx, where there are various ways to import the same crates.

```rust
// consensus/types/src/lib.rs
pub use bls::{
AggregatePublicKey, AggregateSignature, Error as BlsError, Keypair, PUBLIC_KEY_BYTES_LEN,
PublicKey, PublicKeyBytes, SIGNATURE_BYTES_LEN, SecretKey, Signature, SignatureBytes,
get_withdrawal_credentials,
};
pub use context_deserialize::{ContextDeserialize, context_deserialize};
pub use fixed_bytes::FixedBytesExtended;
pub use milhouse::{self, List, Vector};
pub use ssz_types::{BitList, BitVector, FixedVector, VariableList, typenum, typenum::Unsigned};
pub use superstruct::superstruct;
```

This PR removes these re-exports and makes it explicit that these types are imported from a non-`consensus/types` crate.


Co-Authored-By: Mac L <mjladson@pm.me>

beacon_node/lighthouse_network/src/rpc/protocol.rs

@@ -1,5 +1,6 @@
 use super::methods::*;
 use crate::rpc::codec::SSZSnappyInboundCodec;
+use bls::Signature;
 use futures::future::BoxFuture;
 use futures::prelude::{AsyncRead, AsyncWrite};
 use futures::{FutureExt, StreamExt};
@@ -20,7 +21,7 @@ use types::{
     EmptyBlock, Epoch, EthSpec, EthSpecId, ForkContext, ForkName, LightClientBootstrap,
     LightClientBootstrapAltair, LightClientFinalityUpdate, LightClientFinalityUpdateAltair,
     LightClientOptimisticUpdate, LightClientOptimisticUpdateAltair, LightClientUpdate,
-    MainnetEthSpec, MinimalEthSpec, Signature, SignedBeaconBlock,
+    MainnetEthSpec, MinimalEthSpec, SignedBeaconBlock,
 };
 
 // Note: Hardcoding the `EthSpec` type for `SignedBeaconBlock` as min/max values is