Create a simple NewBlockTemplate that creates a block template and inserts the coinbase in one -- one sided coinbase

[stringhandler]

The current 2 step process of creating a block template is inefficient and means that there could be a delay for miners. Mining nodes that have implemented a better get_template will win more blocks, so it should be as efficient as possible

[SWvheerden]

The biggest issue we have here is the private key.
We need some unique key generation here.
Either

• we need to send over a private key with grpc
• add in a default wallet to call from the base_node
• add a built-in wallet to the base node
• provide the seed key so the base node can construct the correct key.

[SWvheerden]

If the Miner can calculate the MMR roots, then we can do it in a single call.
Problem with this however is that to calculate new MMR roots, the miner needs a copy of the entire pruned set of the MMR.

[SWvheerden]

This is very much solved by make the coinbase transactions one-sided.

We can use two methods on this: normal 1-sided or even stealth-1-sided.
We can only use the HW wallet method as per RFC 205 -> tari-project/rfcs#98