Specified diagnostic for iterating known array type without --downlevelIteration

[JoshuaKGoldberg]

Fixes #16022

If an entity can't be iterated for lack of a [Symbol.iterator] and is one of a few known array-like types that would receive it in --downlevelIteration, a more specific error message indicating so is now emitted.

I think an ideal solution would have been to check whether the type would be iterable in a higher output target, but I couldn't find prior art in code for doing so. Is there a better way to check for this case, or an existing or larger list of known names?

Refactors the big multi-level ternary previously used to generate the diagnostic message because it would have been even more multi-level from this change. Teeny improvement: yieldType isn't calculated unless it's needed now.

[sandersn]

Looks good save a couple of nitpicks. I think a static list of types is fine because I doubt the list will expand much over time.

[sandersn]

I'll merge this for 4.2 after 4.1 RC gets its own branch.

[DanielRosenwasser]

@sandersn were you still going to merge this?

[sandersn]

Sorry, I forgot about this. I merged from master, and I'll merge the PR when tests finish running.