chore(eslint-config-pie): DSW-2294 upgrade eslint to v9

[xander-marjoram]

Describe your changes (can list changeset entries if preferable)

• Upgrade eslint to v9
  • Remove .eslintignore files (replace in new config format, if required?)
  • Reformat .eslintrc.js files to flat eslint.config.js format.
    • We may be able to do a partial migration to start with, by disabling flat config files?

---

• Waiting on Airbnb to support v9
• Update example apps (currently untested)
• Make sure unit tests are correct (likely need to wait for Airbnb config to be updated)
• Fix unit tests for strict config
• Fix framework (Vue) exports
• Make sure all eslint-disable comments are still needed (I think you can add a linting rule for this?)

Author Checklist (complete before requesting a review)

• I have performed a self-review of my code
• I have added thorough tests where applicable (unit / component / visual)
• If changes will affect consumers of the package, I have created a changeset entry.
• If a changeset file has been created, I have used the /snapit functionality to test my changes in a consuming application

[changeset-bot]

⚠️ No Changeset found

Latest commit: d9a5c5a

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