[Post-7.0] Improve readability of `Array.from` / `TypedArray.from` `mapFn` parameters

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Currently, the `mapFn` argument of `Array.from()` is typed as `(v: T, k: number) => U`.
However, when this information is displayed in an IDE tooltip, it is difficult to grasp what values are passed to `v` and `k`.

To improve clarity, I propose changing the type definition to `(element: T, index: number) => U`, following [the description of the same method in MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from). The same applies to TypedArray.from().

Supplementary Information:
- The target file is `internal/bundled/libs/lib.es2015.iterable.d.ts#L107`.
- These changes are not intended to fix differences between 6.0 and 7.0, and according to `CONTRIBUTING.md`, the Pull Request should be submitted after the 7.0 release. I plan to submit a Pull Request for this once 7.0 is released.

Inizia da internal/bundled/libs/lib.es2015.iterable.d.ts#L107 e individua le dichiarazioni di mapFn di Array.from e TypedArray.from. Confronta i nomi dei relativi parametri con la descrizione MDN collegata, quindi conferma che entrambe le dichiarazioni usano nomi descrittivi per l'elemento e l'indice senza modificarne i tipi o il comportamento.

Scritto dal modello di indicizzazione a partire dal testo della issue.