Bug: prefer-spread shouldn't encourage iterating over strings

[JoshuaKGoldberg]

prefer-spread reports on String#split(''), fixing to a typical .... That matches the design of string iterability as it was originally intended. However, allowing primitives to be iterated over is widely considered a mistake: https://github.com/tc39/how-we-work/blob/main/normative-conventions.md#reject-primitives-in-iterable-taking-positions.

Proposal: can eslint-plugin-unicorn remove the preference of String#split('') from prefer-spread?

const text = 'hello 👋';

text.split(''); // "fixed" to [...text]

I'm roughly quoting @Josh-Cena from this discussion: https://github.com/typescript-eslint/typescript-eslint/pull/8509/files#r1781707713. Context: in typescript-eslint, we're implementing typescript-eslint/typescript-eslint#748 Rule proposal: prevent array, iterable and function spreads into objects. The rule is set to report on ...string by default... and then unicorn/prefer-spread reports on String#split(''). You can't win!

[Josh-Cena]

I do appreciate that this is a virtually impossible task to be done correctly by default. .split("") is wrong but so is ..., just on different levels. JS should really expose iterator getters like .graphemes(), .graphemeClusters(), etc... But for now, either removing the suggestion or recommending Intl.Segmenter makes more sense. Alternatively, in our rule, we can add docs for disabling checking string spreading.