fix(select): remove list action button from scrollable area in select list

[edleeks87]

fix #6541

Proposed behaviour

Adds a new scrollable container to the select list so that the list action button is no longer within the scrollable area.

Current behaviour

List action button is included within the scrollable area in select list

Checklist

• [x] Commits follow our style guide
• [x] Related issues linked in commit messages if required
• [x] Screenshots are included in the PR if useful
• [x] Unit tests added or updated if required
• [x] Playwright automation tests added or 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