feat!: add pool and tari difficulties to sha3 miner and merge mining proxy

[hansieodendaal]

Description

• Added pool and tari difficulties to the p2pool request.
• In p2pool mode, the SHA3 miner and the merge mining proxy will submit the block to the base node if the achieved difficulty equals or exceeds the Tari target difficulty.
• Since the SHA3 miner and the merge mining proxy (the latter only if enabled in config) always calculate the achieved difficulty; it is now included in the SubmitBlockRequest as an option so that the local p2pool node does not have to recalculate it if provided.

Edit

• For the merge mining proxy, evaluate the best block hash to decide if a new tari template must be requested. In re-orgs where the height will be the same as before the re-org, only checking height is insufficient.
• Added pertinent information to proxy log messages.

Motivation and Context

When implemented fully in sha-p2pool:

• Improved efficiency overall in submitting blocks to the base node.
• Improved efficiency for the p2pool node internally when evaluating local blocks.

Edit

• Many orphans were observed in the Tari blockchain when doing merged mining with sha-p2pool.

How Has This Been Tested?

Currently, all unit and cucumber tests pass as those run without p2pool mode. A combined system-level test is required when this is implemented.

What process can a PR reviewer use to test or verify this change?

Code review.

Breaking Changes

• [ ] None
• [ ] Requires data directory on base node to be deleted
• [ ] Requires hard fork
• [X] Other - Please specify

BREAKING CHANGE: gRPC SubmitBlockRequest interface change that will impact sha-p2pool.