Components: polish ToggleGroupControl

[ciampo]

Description

This PR is a refactor of the ToggleGroupControl component:

• Update the folder structure and the READMEs to follow the latest guidelines
• Add JSDocs to the exported components
• Embed the ToggleGroupControlButton component directly into the ToggleGroupControlOption component, as proposed in Fix ToggleGroupControlOption not passing ref to the underlying element #35546 (comment)

Tracking changes commit-by-commit may offer an easier way to review this PR.

I will potentially follow-up with another PR splitting the code in each component.tsx into a separate hook.ts file, as per the guidelines

How has this been tested?

There should be no runtime behavioural changes:

• Project should build with no TypeScript errors
• Tests should pass
• Storybook examples should work the same way as in production

Types of changes

Refactor / tidy up

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[ciampo]

I had to update this type from

WordPressComponentProps< ToggleGroupControlOptionProps, 'input' >

to

WordPressComponentProps< ToggleGroupControlOptionProps, 'button' >

because otherwise TypeScript would throw an error on the Radio component, since it has the as="button" prop.

[diegohaz]

LGTM! Thanks for working on this @ciampo!