Match block hash computation from core

[itegulov]

era-test-node uses a placeholder block hash computation function that produce different results from zksync-era.

This is perhaps not easily observable by users hence of lower priority but can still be unexpected if you want to, e.g., manually replicate an existing block from mainnet.

Another blocker is that this likely requires a significant refactor of metadata_calculator as it is designed around PG connections.