PPLNS with job declaration

The primary justification for this feature is to prevent pools from providing false information about share indexes within a slice during challenges. However, this concern may be mitigated by the fact that the path itself suffices to determine the index of a leaf, a task for which the pool is already responsible for providing the necessary data. This suggests a potential redundancy in requiring the share_index to be committed and returned, given that the path information alone accomplishes the objective of index verification without the need for additional mechanisms.