Fix local testnet scripts (#2229)

## Issue Addressed

Resolves #2094 

## Proposed Changes

Fixes scripts for creating local testnets. Adds an option in `lighthouse boot_node` to run with a previously generated enr.

scripts/local_testnet/ganache_test_node.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+source ./vars.env
+
+ganache-cli \
+	--defaultBalanceEther 1000000000 \
+	--gasLimit 1000000000 \
+	--accounts 10 \
+	--mnemonic "$ETH1_NETWORK_MNEMONIC" \
+	--port 8545 \
+	--blockTime 3 \
+	--networkId 4242 \
+	--chainId 4242