Bitcoin Block Constructor and Block Submission

1. Connect to bitcoin RPC

2. GBT with sigwit rules (saved for block.hex building and submission) 

3. Build coinbase and merkle_root (witness commitment must), no extra_nonce

4. Print values (from GBT and coinbase and merkle_root in big-endian and little-endian each)

5. Expect input: nonce in little-endian

6. Build, sterilise and submit block.hex

Must be built strictly as described. AI will not do the job, the use of AI will be identified right away. The freelancer must be an expert in this SPECIFIC process. Budget can reasonably grow if the quality is ensured. The solution must be ready to use and will be rigorously checked strictly in mainnet.