A trait to clear the container, for cases when caching may need to be temporary during some
calcuations, but may grow unbounded over the course of the program otherwise.
A trait to reserve space in a container, in case you know how many values are about to enter
and can avoid reallocations by reserving more space at once.
A generic trait for anything that would like to be used in a [GenericCache], allowing easy
extensibility using a container not covered by this library.