Combine ArrayLiteral, MRHS, QSymbols, QWords, Symbols, Words into ArrayNode

All of these nodes are effectively arrays. We should combine them. YARP has:

* `elements` - the list of elements in the array
* `opening_loc` - the source range representing the opening (e.g., `[`, `%w[`, or omitted)
* `closing_loc` - the source range representing the closing (e.g., `]`, `}`, or omitted)