[prefix-trans] implement store upgrade handler for gov module

[haozhan9]

1. check all the keys and values of Shield module to identify the existence of "certik" address prefix
2. Change the "certik" prefix to "shentu"
3. modify the test code to cover both "certik" prefix and "shentu" prefix
4. if appliable, modify the corresponding simulation code to cover both "certik" and "shentu" cases