fix(textbox, select, textarea): ensure width is maintained when a flex item

[nuria1110]

fix #7718

Proposed behaviour

Add width: 100% to Select, Textbox and Textarea outermost container to ensure they extend to maximum width available.

Current behaviour

Select, Textbox and Textarea components default to minimum content width when they are flex items.

Checklist

• Commits follow our style guide
• Related issues linked in commit messages if required
• Screenshots are included in the PR if useful
• All themes are supported if required
• Unit tests added or updated if required
• Playwright automation tests added or updated if required
• Storybook added or updated if required
• Translations added or updated (including creating or amending translation keys table in storybook) if required
• Typescript d.ts file added or updated if required
• Related docs have been updated if required

QA

• Tested in provided StackBlitz sandbox/Storybook
• Add new Playwright test coverage if required
• Carbon implementation matches Design System/designs
• UI Tests GitHub check reviewed if required

Additional context

Testing instructions

See https://stackblitz.com/edit/parsium-carbon-starter-nglktc7h?file=src%2FApp.tsx for issue demo.
See new story InFlexContainer for fix.