Allow to select new "Preferred Sequencer" for based sequencer

[citizen-stig]

Intro

Currently preferred sequencer only set during genesis and not allowed to be changed, only removed.

Desired outcome

Design on how new perferred sequencer should be decided. Should be nominated by existing preferred sequencer? Or if there's no preferred sequencer, should there key of rollup deployer stored, so they can change it?

Should there be voting by existing sequencers?