Add toledo support (#1874)

## Issue Addressed

NA

## Proposed Changes

Adds support for the [Toledo](https://github.com/protolambda/toledo) dev-net.

```bash
lighthouse --testnet toledo bn --http
```

This is for development only, we do not recommend users to join this testnet.

## Additional Info

- ~~Blocked on #1862~~

common/eth2_testnet_config/build.rs

@@ -1,7 +1,7 @@
 //! Downloads a testnet configuration from Github.
 
 use eth2_config::{
-    altona, medalla, spadina, zinken, Eth2NetArchiveAndDirectory, GENESIS_FILE_NAME,
+    altona, medalla, spadina, toledo, zinken, Eth2NetArchiveAndDirectory, GENESIS_FILE_NAME,
 };
 use std::fs::File;
 use std::io;
@@ -12,6 +12,7 @@ const ETH2_NET_DIRS: &[Eth2NetArchiveAndDirectory<'static>] = &[
     medalla::ETH2_NET_DIR,
     spadina::ETH2_NET_DIR,
     zinken::ETH2_NET_DIR,
+    toledo::ETH2_NET_DIR,
 ];
 
 fn main() {