Optimize block processing performance by caching justifications map

[noopur23]

Block processing times are high. One of the reason is the repeated creation of justifications for each block.

Implement a caching mechanism for the justifications map that gets produced during block processing. Add a cache_justifications flag that allows cloning and reusing the justifications map from the parent state instead of regenerating it from scratch for each new block. This should substantially reduce processing overhead and improve block validation times.