Refactor abilities for characters

[cdsupina]

Refactor abilities into "trait objects" https://doc.rust-lang.org/book/ch17-02-trait-objects.html#defining-a-trait-for-common-behavior

Character components can each have an ability property containing a struct that implements the ability trait. It would resemble the following.

pub struct CharacterComponent {
    pub ability: Box<dyn Ability> ,
    ...
}

Structs implementing the ability trait could share common functions related to cooldowns and execution.