Migrate the existing PBFT consensus to a Rollup-style sequencer architecture

## Background
This is the first phase for https://github.com/morph-l2/morph/issues/846, migrating PBFT consensus to a centralized sequencer, while maintaining compatibility with both the legacy and the new block production logic.

## Reference
https://larkfive.sg.larksuite.com/wiki/EE2FwFjmzi7mNlkTkVJlguXFgUh