Implement history expansion (word designators, event designators)

[reubeno]

In bash, there's a set of non-$ expansions (e.g., !!) that will expand based on the current shell history. None of this is implemented in brush as of yet.

This will need to go into word expansion. Some work may need to be done to better integrate shell history into the core brush crate; right now much of it is handled by brush-interactive.