`HistoryArray` is a very specific name and it doesn't tell the reader what
it *really* means unless you read its code or the docs of the class.
On the other hand, `Ring` is a [very well-known term][1], which means exactly
what `HistoryArray` does. The alias name for it is circular buffer. I chose
`Ring` because it is shorter and used by Golang, so I expect programmers to
be familiar with `Ring`.
[1]: https://en.wikipedia.org/wiki/Circular_buffer