Limit side effects of polyfills loaded for config/I18n

[romaricpascal]

What

Ensure only components needing the dataset, closest and possibly trim polyfills import them. This'll help reduce bundle size for non-configurable or non-internationalisable components.

Possible approach could be to:

• make a separate module for closestAttributeValue that imports Element.prototype.closest
• make a separate module for normaliseString that imports String.prototype.trim
• import Element.prototype.dataset in all components requiring configuration as they access the dataset. Given that one will be an easy one to miss, I wonder if we shouldn't have a getDataset function that has side effect.

These files could live in an src/polyfilled folder that we'll revisit for v5.

Why

@colinrotherham wrote a neat explanation in this comment: #2887 (comment)

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• Polyfills don't burden components that don't require them when the components are imported individually