miscelaneous fixes on syncing, rpc and responding to peer's sync related requests (#3827)

- there was a bug in responding range blob requests where we would incorrectly label the first slot of an epoch as a non-skipped slot if it were skipped. this bug did not exist in the code for responding to block range request because the logic error was mitigated by defensive coding elsewhere
- there was a bug where a block received during range sync without a corresponding blob (and vice versa) was incorrectly interpreted as a stream termination
- RPC size limit fixes.
- Our blob cache was dead locking so I removed use of it for now.
- Because of our change in finalized sync batch size from 2 to 1 and our transition to using exact epoch boundaries for batches (rather than one slot past the epoch boundary), we need to sync finalized sync to 2 epochs + 1 slot past our peer's finalized slot in order to finalize the chain locally.
- use fork context bytes in rpc methods on both the server and client side

beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs

@@ -298,8 +298,8 @@ impl<TSpec: EthSpec> Decoder for SSZSnappyOutboundCodec<TSpec> {
             .rpc_response_limits::<TSpec>(&self.fork_context);
         if ssz_limits.is_out_of_bounds(length, self.max_packet_size) {
             return Err(RPCError::InvalidData(format!(
-                "RPC response length is out of bounds, length {}",
-                length
+                "RPC response length is out of bounds, length {}, max {}, min {}",
+                length, ssz_limits.max, ssz_limits.min
             )));
         }
         // Calculate worst case compression length for given uncompressed length
@@ -439,6 +439,9 @@ fn context_bytes<T: EthSpec>(
                     SignedBeaconBlock::Base { .. } => Some(fork_context.genesis_context_bytes()),
                 };
             }
+            if let RPCResponse::BlobsByRange(_) | RPCResponse::BlobsByRoot(_) = rpc_variant {
+                return fork_context.to_context_bytes(ForkName::Eip4844);
+            }
         }
     }
     None