Improve modeling token nodes

With @ahoppen we identified potential confusion and overcomplication in code relating to modeling token nodes. Specifically, we're currently trying to collapse multiple token kinds into a single one without indicating this in our variable names.

> The only non-trivial place that needs to be updated is `Child.type` in `SyntaxBuildableChild` and, IMHO, the confusion stems from the fact that we try to collapse multiple token kinds into a single one without giving any indication of doing so in the variable names.
>
> I think the way to go about fixing this is to change the associated value of `SyntaxOrTokenNodeKind.token` to `[TokenChoice]`. Then we won’t need to call `Child.tokenKind` in `Child.type` anymore and could shift the computation that’s currently done in this property down to uses where there’s a lot more context. Potentially, the computation might also just become a lot simpler once we see that context.

_Originally posted by @ahoppen in https://github.com/apple/swift-syntax/pull/2006#discussion_r1285082312_

In relation to issue #1978, changes were made in PR #2006 to the Child.tokenKind implementation. However, this solution still appears to be incorrect and needs further attention, which this issue aims to address.