refactor: try to io.Reader/io.Writer while dealing with Genesis

[ilgooz]

modification or generation.

This affects the pkg/cosmosutil and maybe also other places. Let's find out all of them.

Also, create a single cosmosutil.UpdateGenesis(path, options...) to be able to update multiple fields inside genesis. And deprecate SetChainID, SetLaunchTime like funcs in favor of this new func.

These needed because genesis files can get big(100MB and more). Right now we are passing a whole genesis around as bytes.