[generics-rep] Add algorithmic complexity notes

[matthewleon]

Haven't really looked at the other generics, but for Enum, at least, it would be nice to have a note regarding the algorithmic complexity of the generic methods.

[matthewleon]

Just looked at Bounded, and that one might also surprise people.

[matthewleon]

(though I guess in the case of Bounded, the algorithm only runs when the VM first executes the script? Haven't checked.)