chore(ctb): Add comments, rebuild

fix(ctb): Refactor and fix the L2 bridge tests

fix(ctb): Ensure consistent event ordering using super

The _emit methods in child contracts now use super to
call emit the new events.
The legacy events now always precedes the new event.

test(ctb): Use kwargs syntax in _preBridgeX() funcs

chore(ctb): Improve doc comments on _emit funcs