Sequencer verification and rotation

## Background
This is the 2nd phase for implementing https://github.com/morph-l2/morph/issues/846. 
Enable nodes verifies block signature signed by valid sequencer, and support for sequencer rotation for security.

## Reference
https://larkfive.sg.larksuite.com/wiki/MW1Yw829ziw57ukyzKjlV9cpguc