Consistency tests and testing framework

This task will be tricky, challenging, but interesting.
Firstly, I think it's better to read the [documents](https://github.com/casbin/casbin-mesh#cluster) about setting up a cluster. Then, some relating [tests](https://github.com/wildarch/jepsen.rqlite/blob/main/doc/blog.md) may also be helpful.
If some concepts confuse you, check the course [MIT 6.824](https://pdos.csail.mit.edu/6.824/schedule.html) may be helpful.