Minimum Block Height HTTP Headers

[digorithm]

As more RPC providers begin offering Fuel APIs, we will encounter race conditions depending on users' locations, network latency, etc. We want SDK users to specify a “minimum block height” parameter in their requests to work around this.

If the value is provided, it should populate a new HTTP request header called “Minimum-Block-Height.” This value should be submitted with the HTTP request. The node can then reject the request or queue it while it waits for its internal state to catch up.

If a user uses this feature, we should also expose a timeout value if the node decides to queue the request.