Add a nested compound predicate feature when fetching

[ABridoux]

Currently, the fetch request predicate specification only allows flat compound predicates:

Player.request()
    .all()
    .where(\.name == "Toto")
    .and(\.age, .isIn(20, 30, 40))
    .or(\.score > 400)

Doing so, the predicate is name == "Toto && age IN {20,30,40} OR score > 400.
There is no way to specify this predicate: name == "Toto && (age IN {20,30,40} OR score > 400).
The goal is to add nested compound predicates, either by adding the possibility for an and predicate function to have another compound operator, or with another way.