1. Use pre-installed host rust toolchain
2. Build reference/performance fullnode in same part to avoid rebuilding libraries
3. Merge scripts into same part
Now that the Bank is single-threaded again, we can spin up new
accounts on the fly without concern of thread contention. Likewise,
we can send all transactions from a single account, which was also
problematic in the multi-threaded bank. Sending from one account will
also make client-demo straightforward to port to solana-drone.