IDEA: Auto generate Monoid[FunctionN]

Currently cats provides a Monoid instance for Function0 & Function1: https://github.com/typelevel/cats/blob/main/kernel/src/main/scala/cats/kernel/instances/FunctionInstances.scala#L109
While these are very useful, it is not uncommon in Scala to have functions of higher arities like Function2.
And, for all I can see, the implementation of such instances is just mechanical repetition.

Thus, this issue proposes the inclusion of the generation of all the repetitive code from trait Semigroup[Function2] until trait Monoid[Function22] extends Semigroup[Function22]
AFAIK the only downside of such a proposal is the increase in the JAR size; but, personally, I think this is a good addition since not having those instances can be surprising and somehow inconsistent.

PS: I see that we also have Group instances for Function0 & Function1. However, I am unfamiliar with that typeclass and I am not totally sure if such instance is valid for higher arities and if the implementation is equally mechanical; for how the code looks like it seems so, thus I leave it open to also include those in the generator.

Start with the linked kernel/src/main/scala/cats/kernel/instances/FunctionInstances.scala and compare the existing Function0 and Function1 instances. Investigate how higher-arity instances could be generated and whether Group is valid beyond Function1. Done means the agreed generator produces Semigroup and Monoid instances through Function22, with Group included only if confirmed.