Set up a stable Multi-miner Testnet for Nakamoto 3.0

[saralab]

All our current pre-launch Testnets use a signle miner setup, to properly test Nakamoto 3.0, we need a multi miner testnet.
This testing environment should have the following configuration :

• Each signer is connected to a different stacks-node
• Multiple miners (4)
• 1 API follower independent of A and B
• 4 minute bitcoin blocks, with some variance.

Success criteria for this Testnet set up to be marked successful and complete for atleast 1 week:

• No restarts, no resets.