Add Macro for Action Chaining

[Bennett-Petzold]

Adds the act_nest! macro, which allows the tuple macros to be chained for >2 actions without heavily repeated boilerplate.

Example usage:

act_nest!(
    RaceAction::new,
    AlwaysTrue::new(),
    AlwaysTrue::new(),
    AlwaysTrue::new(),
    AlwaysTrue::new(),
    AlwaysTrue::new()
)