Refactor: Refactor app package

[GNaD13]

Currently, we put all registry module logic in a single file app.go. This is very old style and a bit chaotic when importing more module. Should we open a PR to wasmd repository to update new app package style?

[ducphamle2]

imo we don't need to refactor it for now. We are forking from wasmd, so refactoring will cause lots of conflicts down the line