[FEATURE]: Implement propose_block RPC

[sgerbino]

Is there an existing issue for this?

• I have searched the existing issues

New feature

We want to implement a new API call specifically for the block producer to use when proposing new blocks. Unlike submit_block, we want to continue to processing a block despite a failed transaction in order to return a list of failed transactions for the block producer to handle. This new API is considered privileged and therefore should be blacklisted from public use outside the node.

• Break out submit_block into common code that is used by both propose_block and submit_block
• Create a new intent enum called block_proposal which will indicate that we want to process the block the "new way"

Note: If the block fails, the response should NOT contain a block receipt (shall contain offending transactions). If the block succeeds, we should attach the block receipt and it shall not contain any offending transactions. The presence of a block receipt should be reliably used to indicate success or failure.

Anything else?

No response