Also some changes to please clippy

I found that the program slows down quite a lot when N >= 30
Talking with coworkers, they notice a slowdown too but not that big.
So here I am reading and thinking about each
line of code of my recursive function
trying to spot a really costy operation.

First try is minimizing Copy calls by passing
a pointer for n and verbose and not their value. So that there's
only one spot in the memory that is used for them.

With subcommands that'll let the user choose how to solve
the nqueen problem