Add support for futurenet in the network parameter (RPC-only)

[cjonas9]

What problem does your feature solve?

Currently, the network parameter for RPC only supports pubnet and testnet. If one wishes to deploy a futurenet instance, they must manually configure these parameters:

• HISTORY_ARCHIVE_URLs
• NETWORK_PASSPHRASE
• CAPTIVE_CORE_CONFIG

What would you like to see?

The option/flag --network "futurenet" should successfully deploy a futurenet instance by automatically filling in the above parameters. The behavior should match analogously to pubnet and testnet (see the PR).

What alternatives are there?

[N/A]