test(button): refine testing suite

[paulrobinson88]

Proposed behaviour

• Removed Playwright testing where tests are either covered in Jest or Chromatic tests.
• Added 2 tests to Jest for onKeyDown and onBlur callback behaviour.
• Consolidated Accessibility testing where the same variant was tested more than once.
• Removed no longer used code in the components.test-pw file.

Current behaviour

There are a number of Playwright tests which are no longer needed which are causing a loss of efficiency in the testing suite of the repo.

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

Check tests pass correctly.

[edleeks87]

comment: I'm not sure there's anything being tested here that hasn't already be sufficiently covered elsewhere