feat(styles): add default feature flag config

[joshblack]

Closes #9927

Update our usage of feature flags in the project. This also updates our storybook to correctly initialize feature flags.

Changelog

New

Changed

• Add feature flag side effect import to storybook
• Add default feature flag config for styles
• Update feature-flag-enabled usage in notification to use feature-flags
• Update toggle to use feature-flags namespace
• Update Sass to latest version

Removed

Testing / Reviewing

• Verify that the toggle story renders as expected in the carbon-react-next storybook
• Verify tests pass as expected

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[netlify]

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[tay1orjones]

Notifications and Toggle look good in the next storybook 👍

[sstrubberg]

🚀