feat(consensus): Change meta.score and meta.accumulated_weight to int type

[msbrogli]

Motivation

The metadata accumulated_weight and score are calculated summing up the vertices' weight. Even though both metadata can be integer numbers, they are calculated as the logarithm of their integer value. This might lead to minor issues caused by precision error. We currently use the calculate_min_significant_weight() to prevent precision error on mining activity.

This PR converts both metadata to integer values, simplifying parts of the code that had to take float precision into consideration.

Acceptance criteria

1. Change meta.score and meta.accumulated_weight to type int.
2. Change the calculation of meta.score to use weight_to_work().
3. Change the calculation of meta.accumulated_weight to use weight_to_work().
4. Change the consensus algorithm to do direct comparisons (instead of comparisons using WEIGHT_TOL).
5. Replace sum_weights(a, b) to weight_to_work(a) + weight_to_work(b).
6. Replace sum_weights(score, a) to score + weight_to_work(a).
7. Replace sum_weights(accumulated_weight, a) to accumulated_weight + weight_to_work(a).
8. Remove sum_weights().
9. Serialize meta.score and meta.accumulated_weight as strings to prevent precision issues with JSON parsers.

[github-actions]

Bencher Report

Branch	feat/score-acc-weight-types
Testbed	ubuntu-22.04

Click to view all benchmark results

Benchmark	Latency	Benchmark Result nanoseconds (ns) (Result Δ%)	Lower Boundary nanoseconds (ns) (Limit %)	Upper Boundary nanoseconds (ns) (Limit %)
sync-v2 (up to 20000 blocks)	📈 view plot 🚷 view threshold	101,412,264,859.14 (-0.43%)	91,669,666,935.48 (90.39%)	112,040,704,032.25 (90.51%)

🐰 View full continuous benchmarking report in Bencher

[msbrogli]

Approved!

[jansegre]

Just as a report, last night I synced a node from scratch using this branch, it synced correctly up to the same block as the network, and this is a comparison of the score of the best block (which accumulates tiny errors in the current release):

# my node
❯ curl localhost:9080/v1a/transaction\?id=0000000000000000046147a92a42b4e2f50ef587ecb17775efda3628150f2c32 -s | jq .meta.score
88.71139817081715

# public node
❯ curl https://node2.mainnet.hathor.network/v1a/transaction\?id=0000000000000000046147a92a42b4e2f50ef587ecb17775efda3628150f2c32 -s | jq .meta.score
88.71139817083098

Even after the tiny accumulated errors the difference is currently minimal. I'm going forward with the merge.